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  • 1.
    Lagerlund, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Grout Development and Methods for Remedial Grouting of Embankment Dams2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An embankment dam can be damaged by internal erosion. During this process, the soil material erodes and is transported out of the dam structure. Some common types of damage due to internal erosion are piping, less dense soil zones, and zones where the fine material has been washed out.

    To prevent ongoing internal erosion from developing into a damage or a breach, injection grouting may be performed to replace the eroded soil material. In an embankment dam, injection grouting is usually performed vertically. A pipeline is drilled from the crest of the dam to the damaged zone, to which the grout material is delivered via a pump. The injection grouting methods suitable for embankment dams are compaction and permeation grouting. In compaction grouting, a lowmobility grout material is injected at high pressure, compacting the surrounding soil. In permeation grouting, the injection pressure is lower and the grout material flows more easily, allowing it to permeate the porous structure of the soil into which it is injected.

    A grout material for embankment dams should have properties, i.e., particle size distribution, water content, shear strength, and bulk density, similar to those of the original core soil after injection. A grout material with these properties will however be very stiff and difficult to pump, and permeation will be difficult to achieve. Therefore, a new type of non-hardening grout material has been developed and tested in the laboratory. The grout material is a low-mobility grout, but its viscosity and yield strength can be temporarily lowered by replacing the fine aggregates with a limestone filler and by adding a superplasticizer. After injection, the effect of the superplasticizer wears off, leaving a grouted zone with geotechnical characteristics similar to those of the original core soil. The grout material consists of 0–4 mm aggregates, limestone filler, dry bentonite powder, water, superplasticizer, and an air-release agent. The grout material properties and the influence of injection method were tested in three laboratory investigations and the results were presented in four papers.

    Development, and fresh and hardened properties of the grout material were investigated in Paper I. The key findings are: (1) The grout material attracted air when homogenized. When homogenized longer than 15 minutes, it was difficult to pump. Air content up to 16.5 % was observed. (2) After 34 days of storage, the water content was ~10 % and the bulk density ~2250 kg/m3, which are very similar to those of the core soil. The undrained shear strength was ~13 kPa, which was initially lower than that of the core soil but it slowly increased with time.

    The factors affecting a grout material’s ability to permeate a core soil damaged by internal erosion were investigated in a pilot-scale permeation test series and the results are presented in Paper II. Three different coarse-grained materials with d15of 35, 75, and 110 mm were grouted. The key findings are: (1) The ratio between limestone filler and aggregates in the grout material greatly influenced the permeation. A grout material with a ratio of 1.7 performed far better than a grout material with a ratio of 1.4. (2) A higher consistency measurement of the groutmaterial (150 mm vs. 100 mm) improved the permeation if low injection pressure was used. At higher pressure, the role of consistency was minor. (3) A higher maximum particle size, Dmax, of the grout material (4 mm compared to 2 mm) improved the permeation. The difference was most probably caused by higher viscosity and higher yield strength of the grout material with Dmax = 2 mm compared to that with Dmax = 4 mm. The lowest ratio between the minimum particle size of the coarse-grained material and the maximum particle size of the grout material was 4, and using higher pressure, the grouting was successful. Ratios below 4 were not tested.

    From Paper II, the most suitable materials for permeation grouting were chosen to be investigated further for their resistance to flow. The results of this investigation were presented in Paper III. Resistance to flow in the pilot-scale permeation test was found to occur within the pipeline and at its exit, where the grout material downflow was redirected 180° to an upward flow. Total frictional losses could be estimated by regarding the grout material flow as Newtonian laminar. Total frictional losses in the 1.3 m length and 0.075 m diameter pipeline during all testswere measured to be 1–67 kPa/m at grout material velocity of 0.01–1.03 m/s. Frictional losses due to the grout material’s permeation of the coarse-grained materials could be estimated with the hydraulic conductivity. The mean hydraulic conductivities in the d15 = 75 mm coarse-grained material, when permeated by the Dmax = 2 mm and 4 mm grout materials, were measured to be 1.7x10-4 and 1.4x10-4m/s, respectively; where as in d15 = 110 mm, the values were 2.1x10-4 and 3.3x10-4m/s. These observed values of the hydraulic conductivity were very close to the expected values. With the Newtonian approach, pressure losses may be easily estimated. This will facilitate the estimation of how much of the grouting pressure at the pump is transferred into the core soil during a grouting operation. The possibility to quantify pressure losses during the permeation of the coarse-grained material with hydraulic conductivities can be used when estimating permeation depths vis-à-vis applied injection pressure.

    The method, “Identification – Localization – Characterization – Remediation”, was tested at the abutment of a large-scale test embankment dam with the newly developed grout material and presented in Paper IV. The seepage rate was successfully reduced to 40 % directly after the injection grouting, and up to 70 % after one year. Most of the seepage reduction was caused by the rotary percussion drilling. Remedial grouting should not be regarded as a last resort, but as a part of a maintenance program.

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  • 2.
    Toromanovic, Jasmina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Monitoring and Modelling of Embankment Dams2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modelling can be used as a tool for prediction of the behaviour of embankment dams as a part of the dam safety work. It is advantageous to predict the performance and compare to measurements done, to obtain more knowledge about the dam behaviour, as these structures are complex and potential failures are hazardous. The research presented in this thesis covers parameter identification by backanalysis, interpretation of dam measurements and numerical predictions of dam behaviour. The research highlights the role of numerical modelling as a supportive tool in dam engineering, ratherthan a standalone technique. Two embankment dams were analysed in the research: a 45 metres high existing hydropower dam and a four metres high experimental dam built during the project.

    The soil materials in an embankment dam vary significantly, as the zones in a dam have different functions. To create reliable numerical models, parameter values defining the stress-strain relationship of the materials are needed. Obtaining such information for existing embankment dams poses challenges, often due to limited available data and the potential risks associated with traditional field sampling methods. In previous research at Luleå University of Technology, inverse analysis was successfully applied to embankment dam calibration of finite element models against field measurements, by utilizing an optimisation code with a genetic algorithm for optimisation. Inverse analysis provides a non-destructive method for obtaining information about the stress-strain relationship of the material in a dam.

    First, applications of inverse analysis are exemplified on an existing embankment dam. The study investigates the impact on the inverse analysis methodology when errors occur in the field measurements. The employed genetic algorithm showed its robustness when dealing with errors, this is important since errors are likely to occur in field measurements. Thereafter, the study examined the usage of parameters identified through inverse analysis in predictions of deformations when a stabilising berm was constructed on the downstream shoulder. The predicted deformations were compared to deformations from inclinometer measurements. The trend of the measured deformations was replicated in the numerical model, and the magnitudes were in the right order. The study shows that predicting future dam behaviour based on results from inverse analysis can be done reasonably well in this case.

    Second, the mechanical behaviour of an experimental embankment dam is interpreted and modelled. Monitoring of pore pressure was done with transducers that were installed at different levels covering the whole core and parts of the filters. Measurements were performed continuously. The response of pore pressure in the core, during impoundment and operation, are focused on. A significant delay of the saturation front was observed, as the pore pressure in the bottom of the downstream part of the core was not building up as expected during impoundment and operation. Fully-coupled numerical analyses were performed, in order to better understand the conditions of the core in the experimental dam. The core was initially assumed to be homogeneous, but the numerical results showed poor agreement with the observed behaviour from field. By further analysing the measurements and modelling, the experimental dam was found to be non-homogeneous, even though it was built under very controlled conditions. Variations in the hydraulic conductivity in the dam core were therefore introduced in the numerical model. The hydraulic conductivity changed with height in the dam, was different in the vertical and horizontal direction and was also changing with time at specific places in the core. With these numerical adjustments better correlations against measurements were obtained, compared to the homogeneous case, indicating that homogeneous conditions are not suitable for the core. The study also showed that the values of parameters obtained from laboratory testing are not suitable for the whole core, as the conditions assumed in laboratory do not correspond to the prevailing field conditions.

    Measurements of the strain development in the bottom of the embankment dam was done by fibre optics. The settlements in the dam body after construction are captured, mainly as areas of higher lateral strain at the toes of the dam. The 1% sloping foundation towards the downstream side is captured. The measurements show that more shear is activated at the downstream side. Impoundment causes the largest strains, it can be observed that the strains vary in the different dam zones the bottom of the dam body.

    In summary, the research presented in this thesis has shown how numerical modelling can be used as support in dam engineering, when combined with monitoring data. Values of parameters that would have been difficult to retrieve otherwise are obtained by inverse analysis, making it possible to perform more reliable predictions. The modelling has also helped to explain unexpected behaviour from monitoring of pore pressure. When the experimental dam was built, it was expected that the core would be homogeneous. The monitoring of the dam and the numerical modelling revealed that the core was non-homogeneous. The experimental dam is small, and it was constructed under very controlled forms. Therefore, it is reasonable to assume that it would be difficult to construct a homogeneous core in a real, large embankment dams. This is an important finding in the thesis, which can influence both how dams should be numerically modelled as well as how dam safety assessments during first impoundment and the beginning of the operation phase should be done.

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  • 3.
    Do, Tan Manh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Excess pore water pressure generation in crushed and fine granular materials under cyclic traffic loads2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Excess pore water pressure can develop in subgrades of railway and pavement substructures due to cyclic loading from heavy traffic, leading to the migration of fine particles into upper layers. This migration can clog pores and diminish the drainage capacity of upper layers,negatively impacting the long-term performance of sub-structures and service life, ultimately risking failure. Therefore, understanding the mechanisms behind the accumulation of excess pore water pressures and the migration of fine particles under cyclic loading is essential for efficient and cost-effective maintenance methods. The main objectives of this research include (1) investigating excess pore water pressure generation in crushed and fine granular materials under cyclic loading, (2) evaluating the migration of these materials into upper layers under cyclic loading, and (3) simulating a practical application using an advanced model to provide valuable insights into the operation of structures subjected to cyclic traffic loads while considering real-world factors from the field.

    A series of cyclic triaxial tests were conducted to investigate the generation of excess pore water pressure in fine granular materials. Two types of fine granular materials, tailings (a crushed material) and railway sand (a fine granular material) were selected for this investigation. The cyclic characteristics of these materials, including cyclic axial strain and excess pore water pressure, were evaluated in terms of number of cycles and applied cyclics tress ratios (CSR). As a result, the cyclic axial strain and excess pore water pressure were observed to accumulate over time due to cyclic loading. However, the extent of accumulation was found to be significantly dependent on CSR values and material types. In addition, a relationship between excess pore water pressure and cyclic axial strain of the fine granular materials was established and proposed based on the results from the undrained cyclic triaxial tests (including both tailings and railway sand samples).

    To assess the migration of fine granular materials into overlying layers under cyclic loading, a modified large-scale triaxial system was employed as a physical model test. A quantitative analysis of material migration was based on the mass percentage and grain size of migrated materials collected at the gravel layer. Additionally, cyclic responses (strain and excess pore water pressure) were evaluated. As a result, the total migration rate of the tailing sample was significantly higher than that of the railway sand sample. The migration analysis on tailings also revealed that finer tailings particles exhibited a greater tendency to migrate into the upper gravel layer compared to coarser tailings particles under cyclic loading. This migration could be attributed to significant increases in excess pore water pressure during the final cycles of the physical model test. The findings from this research could make a valuable contribution to the existing literature concerning the accumulation of excess pore water pressure and its effects on the migration of fine particles under cyclic loading.

    A numerical study was conducted to simulate the complex interactions between tailings materials and cyclic traffic loads on the piers of tailings dams. The integration of experimental data and advanced constitutive models enabled a comprehensive understanding of the behavior of tailings under these loading conditions. The findings focused on the build-up of excess pore water pressures in tailings subjected to cyclic traffic loads while taking into account the effects of truck loads, velocities, and truck resting times. As a result, excess pore water pressures in tailings progressively increased with the number of passing trucks, indicating a cumulative effect of loading cycles. In addition, the effect of truck loads and truck velocities on the excess pore pressure build-up was discovered, with higher truck loads and lower truck velocities leading to increased excess pore pressures, posing a greater risk. Furthermore, through anoptimization process involving variations in truck loads, velocities, and resting times, it was revealed that a combination of increased truck velocity, reduced truck load, and extended truck resting time could effectively minimize the build-up of excess pore water pressures in tailings beneath the pier. These findings offer valuable guidance for optimizing transportation operations on tailings dam piers, enhancing efficiency and safety.

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  • 4.
    Andrén, Anna
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. Trafikverket.
    Freezing Temperature Flows in Railway Tunnels and its Consequence on the Rock Supporting Structure, the Rock and the Reinforcing Elements2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Water in the surrounding rock mass flows into the tunnel via naturally occurring joints and via cracks caused by the blasting used to excavate the tunnel. The most common method in Sweden to reduce or prevent leakage problems are first and foremost the use of grouting. However, experience shows that despite extensive pre-grouting and supplementary post-grouting, it is difficult to seal the rock mass so that drips and moisture are completely eliminated. Although the water itself causes degradation of the tunnel, the degradation process increases dramatically when the water is exposed to freezing temperatures. Water expands during freezing and due to water migration, which occurs in rock in a similar way as in soil, the ice causes frost shattering of the interface between rock and shotcrete and also to the shotcrete and the rock itself. This can damage the main load-bearing system. The ice formation itself is a maintenance problem, as the tunnels must be kept clear of icicles, ice pillars and ice layers in the tracks or on the roads. One of the main tasks in this research project has been to identify which problems cause the most maintenance work and where and when these problems occur in the tunnel.

    During the field observations carried out as part of this doctoral study, many problems with water and ice were discovered, all of which contribute to increased maintenance. Many ice problems are directly linked to frost insulated drain mats. Leakage and ice formations occur at the edge of the drains, in mat splices and when brackets for cable racks, handrails or other installations puncture a drain and it has not been properly sealed. In drains covered with shotcrete, frost shattering and cracking in the shotcrete can be a problem. Frost cycles in the tunnel cause the water to freeze and thaw alternately, allowing more water to reach the freezing area due to water migration, resulting in frost shattering of the rock and the shotcrete. If not anchored with bolts, the reinforcing effect and the stability of shotcrete in a tunnel is dependent on the adhesion to the rock surface. It is, therefore, important to take all available measures to ensure good adhesion. Poor adhesion in itself is not a degradation problem, but a void can form in the interface between rock and shotcrete as a result of poor adhesion. If this void is filled with water that cannot drain away, ice pressure can occur in the layer between rock and shotcrete. The ice pressure can cause cracking and degradation of the shotcrete if the pressure exceeds the tensile strength of the adjacent material. In some of the reported fall-outs of rock and shotcrete, an ice layer was discovered between the rock surface and the edges of the remaining shotcrete layer. Therefore, frost shattering is a likely cause of the fall-outs. Many frost cycles combined with water leakage can cause frost shattering. The field measurements conducted as a part of the doctoral study have shown that most frost cycles do not occur closest to the tunnel entrances, but instead about 100 to 200 m into the longer tunnels. The results from the laboratory tests performed as part of the doctoral study showed that the adhesive strength between rock and shotcrete decreased significantly when the test panels were subjected to freeze-thaw cycles. Furthermore, more of the micro seismic events (AE - acoustic emission monitoring) occurred in the test panels that had access to water during freezing. Therefor, maintenance personnel and inspectors should pay particular attention to water leakage in sections that have an increased number of frost cycles, to avoid future problems with frost shattering of rock or shotcrete. 

    In the longer tunnels studied in this work, a greater number of ice formations occurred in the inner parts of the tunnel, than close to the entrances. The rock mass emits heat, which heats up the cold outside air that enters the tunnel. Due to the heat transfer from the rock mass, leakage points located further along the tunnels can remain unfrozen. A leak that is closer to the tunnel entrances in the longer tunnels or a leak in a shorter tunnel are exposed to higher freezing rates. The entire rock mass freezes and the leak ‘freezes dry’, that is, ice forms in the water-bearing fracture, preventing further water leakage.

    Where and when ice problems occur along a tunnel depends on many factors. Besides the obvious water leakage, the length of frost penetration into the tunnel is the main reason for where and when ice problems occur. The predominant cause of frost penetration in most of the tunnels is the thermally induced airflow. In the longer tunnels, the inclination of the tunnel affects frost penetration the most. The field observations showed that there was a difference in where and when leakage points appear during the year and also in terms of variation in the amount of leakage water. There was also a variation over different years. The conclusions of the field observations are that it is difficult to estimate where the insulated drain mats should be located along a tunnel. Based on experience from this survey, the location of the drains should be determined only after several inspections and especially after a winter period, when the main problems with ice formation occur. Previous perception regarding ice problems have been that ice formation only occurs at the tunnel entrances and in the outer parts of the tunnel. A proposed measure has, therefore, been to cover the first 300 m from each entrance with frost insulated drains to try to completely eliminate the ice problems. However, this is not an effective solution to the problem. The insulation not only prevents the cold from reaching the leakage point, but it also prevents the rock mass from emitting heat that warms up the cold outside air entering the tunnel. Thus, the frost can penetrate further into the tunnel and the problems with ice formation are only moved further into the tunnel. As the amount and location of the frost insulation affects frost penetration, the dimensioning of insulation must, therefore, be carried out in several iterations, where each new distribution of insulation along the tunnel is calculated separately.

    For the tunnels that have been studied as part of this doctoral study, the following has emerged. The central and southern parts of Sweden have shorter cooling periods and the tunnels are exposed to many temperature fluctuations around 0°C during the winter. The frost does not have time to penetrate as far here as in the tunnels in the northern parts of Sweden. Therefore, more ice problems arise around the entrances of the tunnels in the southern parts of Sweden than for those in the northern parts. For northern parts of Sweden, the problem of growing ice formations in sections near the tunnel entrance usually occurs only during the autumn and spring, but not in winter. The field observations showed that the problems with ice growth and temperature fluctuations around 0°C occur further along the longer tunnels in the northern parts of Sweden. This is because the temperature of the tunnel air is higher due to heat transfer from the rock mass. For shorter tunnels that adopt the same temperatures as the outside air, ice formations can occur along the entire length of the tunnel in the sections that have leakage problems. The Swedish Transport Administration’s regulations are currently being updated and the observations and measurements carried out in this doctoral work are now being used to evaluate new requirements regarding frost penetration in tunnels.

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  • 5.
    Nigéus, Susanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Recycling of green liquor dregs in cover application on acid generating mine waste2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mining industry generates massive amounts of waste that without treatment and in contact with atmospheric oxygen can cause the formation of acid rock drainage (ARD). In Sweden, the most common reclamation measure for mine waste is to apply a multi-layer cover on top of the waste deposit. The access to suitable cover-materials is, however, limited and can lead to extensive costs for the mining companies. This creates a driving force for alternative solutions, e.g., bentonite amendment to till. As bentonite production is costly both economically and environmentally, recycling of industrial residues to produce sealing layer material is an attractive option. The recycling is beneficial for the industry generating the residue, the mining industry using the residue and the society in its strive for zero waste. An industrial residue that has potential to improve the sealing properties of local till is green liquor dregs (GLD), a residue from pulp production. The main objective of this study was to, by laboratory studies and field application and evaluations, investigate if green liquor dregs amended till can be used as a sealing layer material on top of acid generating mine waste. The conclusion from the laboratory study is that the hydraulic conductivity does not decrease significantly with GLD addition to the silty till. However, the water retention capacity, which can be seen as the major important feature of a sealing layer to be used on top of sulfidic mine waste by keeping the layer close to saturation, shows significant improvements with GLD addition. In the field study the GLD amended till was applied successfully from a soil mechanical point of view (e.g., the compaction degree after application). The early results from the monitoring of the sealing layer indicate results comparable to the more frequently used bentonite amendment in a sealing layer, with soil moisture values reaching close to saturation. However, this study also concludes that the great variation in GLD, especially regarding its soil mechanical properties such as water content, makes it difficult to use compared to commercial products. The material used in the laboratory investigations in the planning phase of a project might behave differently than the one that is delivered to the minesite for reclamation.

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  • 6.
    Gunnvard, Per
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Timber Pile-Supported Embankments: Arching and Reinforcement2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reduced climate impact is a worldwide strive today. The foundation engineering industry is continuously searching for more sustainable solutions to reduce resource usage and pollutions directly or indirectly. One such solution is timber piling, as an alternative to the commonly used concrete and steel piles. Geosynthetic-reinforced pile-supported embankment (GRPSE) is a common foundation method for settlement reduction of both roads and railways on soft subsoil. Pile-supported embankments rely on arch formation within the embankment material, which transfers the traffic and embankment load onto the piles. Reinforcing of the embankment with geosynthetics further increases this load transfer, whilst also stabilising the formed arches. Substituting concrete and steel piles with timber piles allows for a GRPSE solution with lower carbon footprint, especially if the timber piles are untreated and the (concrete) pile caps are excluded. The lower strength of timber piles and exclusion of pile caps require narrower pile spacing and/or more extensive geosynthetic reinforcement to maintain a stable arch formation in the embankment. Unstable arches can cause unwanted differential settlements in the upper structure of the embankment. Although timber piling is being practiced in countries like United States, Canada, Australia, and the Netherlands, only Sweden has a dedicated code for GRPSE using untreated timber piles. However, the Swedish code is deliberately conservative with narrow required pile spacing and two layers of GR. The aim of the thesis is to improve the resource efficiency and sustainability of geosynthetic-reinforced timber pile-supported embankments, by optimizing the required number of piles and amount of geosynthetic reinforcement (GR) based on the Swedish code.

    First, a numerical study was performed to evaluate the Swedish code with a focus on the pile group. The code states that the timber piles should be installed with a centre-to-centre distance of 0.8–1.2 m in a triangular arrangement instead of the more common square arrangement. Finite element (FE) modelling setups—with square and triangular pile arrangements with varying centre-to-centre distance—were used based on a geosynthetic-reinforced timber pile-supported road embankment to evaluate the design criteria. As part of the evaluation, a state-of-the-art study was done on international design guidelines and analytical models. From the FE simulations, no evident difference of mechanical behaviour is found between the triangular and the square piling pattern. The maximum allowed centre-to-centre distance between timber piles can be increased from 1.2 to 1.4 m, decreasing the number of timber piles by as much as one-third.

    Second, a field study was carried out. A reconstructed road embankment with geosynthetic reinforcement and timber pile support was instrumented in 2020, and the first two years of post-construction data was analysed. Monitoring of the embankment included settlements, pile deflection, pore water pressure, load on piles and subsoil, and strains in the GR. Only small strains were observed in the GR because of minor GR deflections. Partial arch formation was found from the measured load distribution, as less than half of the total load of embankment and traffic was carried by the piles. The pile loads increased in winter as the frost front penetrated the embankment and stiffened the embankment fill. The field study data provides a detailed reference for this thesis and further research on timber pile-supported embankments.

    Third, a numerical study was performed on the effect of geosynthetic reinforcement in timber-piled embankments. Three different cases were studied: two layers of GR (“beam” theory load transfer), one layer of GR (“catenary” load transfer) and unreinforced. The hypothesis is that there exists a range of embankment heights and centre-to-centre pile spacings for which one of the cases is preferrable to the other two in terms of resource efficiency. FE simulations, calibrated using the data from the field, were performed of the three cases with varying pile centre-to-centre spacing, embankment height and subsoil material. Based on the results of the FE simulations and literature on arch formation, limits for the three cases are suggested as a guideline for stable arch formation in timber-piled embankments. The limits allow for a more object-specific design than the Swedish code, improving the resource efficiency both in terms of required number of piles and amount of GR.

    Based on the findings from the three sections presented in this thesis, recommendations are given on timber pile-supported embankments. The recommendations are based on theoretical calculations and field test data. As an outlook, the thesis outlines the design of a physical laboratory test setup to verify the theoretical results and establish implementable recommendations. Though the primary application of timber pile-supported embankments, the physical test results can be extrapolated to pile-supported designs in general.

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  • 7.
    Silva, Ingrid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Investigation of Suffusion in Glacial Till Dam Cores: Testing methods and critical hydraulic gradients2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Suffusion is an internal erosion mechanism that occurs in embankment dams when fine grained particles in the dam core are washed out by seepage. Initiation of internal erosion depends mainly on three major factors: grain size distribution of the soil, stress conditions and hydraulic gradient; whilst its continuation depends on the properties of the filter. Broadly graded moraines, as glacial tills, are more susceptible to internal erosion by suffusion than other types of soils used in dams. Most embankment dams in Sweden consist of a central core of glacial till built more than 50 years ago. At the time of its construction, the available guidelines did not include specific grain size boundaries for the core and the filter related to internal erosion susceptibility. Today, several Swedish embankment dams have experienced incidents of internal erosion such as leakages and sinkholes, making internal erosion an important safety issue. This circumstance leaded to the question: what are the conditions triggering internal erosion by suffusion in embankment dams? This research aims to contribute to the assessment of dam safety by increasing the knowledge on glacial till soils regarding: i) the optimum empirical method to evaluate the susceptibility to suffusion; ii) the effects of boundary and testing conditions in the experimental evaluation of suffusion, and iii) summarize reference values of the hydraulic gradient triggering the initiation of suffusion. The thesis includes a literature review on the existing methods to evaluate soil’s susceptibility to suffusion, a comparison among the difference testing and boundary conditions applied in the experimental assessment of soil’s susceptibility to suffusion, and an experimental study aiming to determine the critical hydraulic gradient for suffusion to initiate in glacial till soils (ic). The experimental study includes three glacial till soils with particle size distributions representing different initial conditions in the core material, e.g.: internally stable, internally unstable and critically internally unstable. The boundary conditions considered in the test program are: initial void ratio, type of filter and specimen size. Test were performed with three different ratio of increase of hydraulic gradient and three different time interval to increase the hydraulic gradient. Results show that the Rönnqvist (2015) adaptation of the Kenney and Lau (1985, 1986) method modified by Li and Fannin (2008) is an accurate empirical method to evaluate the susceptibility of glacial till soils to suffusion. It was also concluded that the critical hydraulic gradient triggering suffusion is not a unique value but depends on the testing conditions, such as axial loading, rate of increase of hydraulic gradient (Δi) and time interval to increase hydraulic gradient (Δt). The higher the axial load the higher the critical hydraulic gradient needed to initiate suffusion. High ratio of increase of hydraulic gradient applied with short time interval can lead to ic - values higher than the obtained in tests with low Δi and long Δt. Tests should be performed with low rate of increase of hydraulic gradient and each hydraulic gradient should last long enough for the specimen to adapt/respond to the new hydraulic conditions. Nevertheless, a general observation is that the critical hydraulic gradient of internally unstable soils tends to be lower than 5 when tested without axial load.

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  • 8.
    Al-Madhlom, Qais
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Potential Use of Aquifer Thermal Energy Storage System in Arid Regions2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    After the Oil Crises in 1973, which meant higher energy costs, the world started to look for other sources of energy. This led to the development of renewable energy techniques. Because of the intermittent nature of renewable energy, storage systems were also developed. Underground Thermal Energy Storage (UTES) systems spread and are now globally well known. In these systems, excess thermal energy (heat or cold) is stored (short term and/or long term) from the surplus period to periods of higher demand. The storage media in such systems are underground materials, e.g. rock, soil, and/or groundwater. The current study aims to examine the use of underground thermal energy storage systems in arid regions, in order to increase the efficiency of both cooling and heating systems in these regions, such that CO2 emissions and consumed electricity for these purposes are reduced. Three main parameters determine which type of Underground Thermal Energy Storage (UTES) systemis most suitable. These are site, design, and operation parameters. The site-specific parametersinclude soil properties and all geo-hydrological, environmental, geological, metrologicalconditions. Therefore, the site parameters cannot be changed after installing the storage system,since they majorly depend on the location, while the other parameters (design and operation) canbe changed after construction. The first primary goal of this study is to find how and what site parameters involved to specify the most suitable type of UTES systems in arid regions. Thus, the suitable type of UTES systems can be decided. The second primary goal is to answer how and where to select the best location to install the adopted system. To achieve the goals of the study, two arid regions within Iraq were used as case studies. They are Babylon and Karbala, where the former is characterized by its shallow aquifer, while the latter is characterized by a relatively deeper aquifer. The ArcMap-GIS software was used to prepare the relevant digital maps, e.g. maps of hydraulic conductivity, population, type of soil, aquifers, groundwater elevation, transmissivity, and slope. Then, the vulnerability (readiness for being polluted by the surface contaminants) maps of the available aquifers were determined, followed by finding the seepage velocity of the groundwater. Depending on the outputs of the vulnerability and the seepage velocity, the most suitable type of Underground Thermal Energy Storage (UTES) systems can be decided. This study, also, includes developing/inventing a general methodology that can be used to determine the best location to install Underground Thermal Energy Storage (UTES) systems, including Aquifer Thermal Energy Storage (ATES) systems. The last part of this study includes applying the suggested methodology to determine the best location to install the suitable type of Underground Thermal Energy Storage (UTES) system in the study area. The first study was in the Babylon Province. Here, groundwater table is very shallow (less than 2 m depth in some regions). The crystalline bedrock is at a depth of 9-12 km below the ground surface, overlaid by 9-12 km of sedimentary rocks on which there is a 2-50 m thick layer of alluvial silty clay sediments. The groundwater moves slowly in this aquifer (2.12*10-6 - 1.85*10-1) m/d, and it is brackish having salinity of 5000-10000 mg/l. The susceptibility (vulnerability) of the aquifer in northern part of Babylon province is low to very low having ranges from 80 to 120 on Drastic model scale, which has the overall range of 26 – 226 (i.e. 0.27- 0.47 on normalized vulnerability). The second study area was a part of Karbala Province. This area can be divided into two regions based on the geology and geo-hydrological conditions. An eastern part is located on the Mesopotamian plain, and a western part is located in Western Desert. In both parts, the groundwater table is relatively deeper than the Babylon province. In the eastern part, it is generally more than 4 mbgs (meter below ground surface). While, in the western part it is deeper and reaches to 48 mbgs in depth. The soil in the eastern part is alluvial silty clay, while the western part consists of gypcrete sandy deposits. The groundwater, which flows towards the east, has a seepage velocity range from 0 to 0.27 m/d. The salinity of the groundwater changes from slightly brackish (1000-3000) mg/l in the western parts to highly brackish (5000-10000) mg/l in the Mesopotamian parts of the province. By comparing the site parameters of each province with the different UTES systems, the type of thermal energy storage system was decided. The most important site parameters are the depth of the water table and the aquifer characteristics. For Babylon Province, the expected suitable underground thermal energy storage system is an aquifer thermal energy storage system in silty clay. For Karbala Province, two systems are suggested: for the eastern part, aquifer thermal energy storage system in silty clay is recommended, while for the western part, a deep (10-30 m depth) sandy aquifer thermal energy storage system is recommended. After that, a methodology was developed and used to determine the suitable location in which to install the Aquifer Thermal Energy Storage (ATES) system. For Babylon province, the site selection index ranges between 2.9 and 5.3 on 1 to 10 scale. About 71% of the region has a site selection index ranges between 4.71 and 5.3. Concerning Karbala study area, the site selection index ranges between 3.1 and 9.1. About 15% of the region has a site selection index between 8.1 and 9.1.The energy saving in neighboring countries to Iraq by using the Aquifer Thermal Energy Storage (ATES) system ranges from 55% to 72%. It is also expected that using a ground sink heat pump instead of a conventional air-to-air heat pump increases the COP (Coefficient Of Performance) of roughly (10) to (-17). The negative sign means that the heat is injected into the ground. More theoretical and field studies are required to cover the different aspects of the subject of potential use of Aquifer Thermal Energy Storage (ATES) system in an arid region, and to verify the improvement of COP (Coefficient Of Performance) due to using these systems.

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  • 9.
    Hassan, Rebwar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sediment Characteristics and Sedimentation Rate Estimation in the Dukan Reservoir2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Dukan Reservoir has been created from the construction of the Dukan Dam on the Lesser Zab River where it crosses the Khalakan Thrust Sheet (Khalakan Mountains) through a gorge 65 km northwest of Sulaimani and 295 km northeast of Baghdad. The Dukan Dam is a multi-purpose dam which was built from 1954 to 1959 to control the flooding of the Lesser Zab River, and to provide irrigation, hydroelectricity, and water storage. Reservoir sedimentation can significantly reduce reservoir storage capacity as dams become older. The Dukan Reservoir has been selected for this study to determine the nature and characteristics of the deposited sediment particles in the reservoir, as well as the estimation of the rate of sedimentation from 1959 to 2014 by using the bathymetric survey and the Soil and Water Assessment Tool (SWAT) model methods.Geologically, the Dukan Reservoir is located in the High Zagros Fold-Thrust Zone (High Folded Zone) of the northwestern segment of the Kurdistan Zagros Fold-Thrust Belt. This reservoir is a natural and structurally controlled depression located in the Btwen (Ranya) Agricultural Plain extending between the Ranya Thrust Sheet (Kewa-Rash Mountains) and the dam body itself. A geological survey was conducted for the study area and it has been concluded that the structural controls were more effective by dividing the Dukan Reservoir into two sub-reservoirs: a bigger triangle-shaped sub-reservoir in the north and a smaller irregularly shaped sub-reservoir in the south. The differences that exist in shapes, lengths, widths, surface areas, and shorelines between the two subreservoirs are also closely related to the structural and stratigraphical controls. The field observations and bathymetric survey indicate that bank sediment erosion is occurring in the two sub-reservoirs, but most of the sediment particles deposition takes place within the bigger sub-reservoir. Grain analyses of the 32 bed sediment samples show that the reservoir bed sediment consists of 15% gravel, 14% sand, 48% silt, and 23% clay. The sediments are composed of silty clay (77.6%), silty sandy clay (10%), sandy gravelly silty clay (1.2%) and gravelly sandy silty clay (1%). The reservoir bed is covered mainly with silt. Both silt and clay percentages increase towards the dam in the smaller sub-reservoir. This is attributable to the decreased water velocity in the reservoir, leading to the deposition of the suspended materials. The sediments are very finegrained, very poorly sorted, strongly coarse skewed, and mesokurtic. The depositedsediment along the Dukan Reservoir can be classified into topset bed (coarse particles) and bottomset bed (fine materials). The slope of the western bank of the reservoir is steeper than the eastern and northern banks. Land slope is the most effective factor in erosion and sediment transport. From the bathymetric survey, it has been also concluded that the minimum elevation which reaches 430 m.a.s.l. is located at the southern part of the bigger sub- reservoir. Based on different bulk densities of the deposited sediment at different water elevations, i.e., 1855 kg/m3 at 470 m.a.s.l., 1855 kg/m3 at 480 m.a.s.l., and 1200 kg/m3 at 480 m.a.s.l., the annual sedimentation rates in the reservoir are estimated to be about 3.8 MCM, 7 MCM, and 6.6 MCM, respectively. This estimation has been supported by the SWAT model method, which shows that the annual sediment load delivered to the Dukan Reservoir from the watershed is estimated to be about 1.3 MCM, representingabout 34% of the total sediments deposited in the reservoir.The reduction in storage capacity of the bigger sub-reservoir from 1952 to 2014 at water elevations 440 m.a.s.l., 460 m.a.s.l, and 480 m.a.s.l. are 72%, 48%, and 24%, respectively. The volume of the deposited sediment is estimated to be around 274 MCM. The percentage of the smaller sub-reservoir area as a percentage of the whole reservoir area varied in 1952 from 4% at water level 520 m.a.s.l. to 100% at 420 m.a.s.l. The author predicts that the estimated annual deposition rate of 6.6 MCM and the projected useful lifespan might extend for another 155 years until 2169, when the sediment will fully occupy the live storages.

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  • 10.
    Rothhämel, Mirja
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stabilization of fine-grained soils in cold environment and exposed to seasonal frost: By-products as hydraulic binders2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis deals with the stabilization of fine-grained soils using by-product originated hydraulic binders. The use of fine-grained soils as subsoil for infrastructure projects is often limited because of the risk for instability. Another reason why building on these soils is not desired is insuÿcient serviceability of the final structure caused by settlements or frost heave that occur in fine-grained soils. Therefore, these soils are often excavated, transported and landfilled. By means of stabilization with hydraulic binder, fine-grained soils can be improved and thereby utilized on site. In case by-products can be used as binders, the method of stabilization combines di˙erent sustainability aspects (reduced carbon footprint of the binder, reduced need of excavation, transport and landfilling as well as quarrying). The method of deep stabilization is often used in Sweden to increase the bearing capacity and to reduce settlements. In countries with more moderate climate than Sweden, stabilization is regularly used also to reduce the frost susceptibility of fine-grained soils in the frost active part of the subsoil.However, the influence of the combination of low curing temperature and freezing and thawing on stabilized soils is unclear, which leads to reduced applicability of this method of stabilization in regions with longer seasonal frost and low annual mean temperature. This thesis focuses on how curing at low temperatures (mean temperature +4› to+7› ) combined with freezing and thawing cycles influences the stabilizing reaction of by-product originated hydraulic binders in fine-grained soil.Three di˙erent combinations of inorganic fine-grained soils with by-product originated hydraulic binders were investigated in laboratory studies. The testing program included curing at +4› for 14, 28 and 90 days, twelve freezing and thawing cycles as well as 28 days of additional curing time after the last thawing. The results of the three laboratory studies were analyzed statistically regarding the varied influence factors (binder content, days of curing before and after freezing and thawing).In a field study, stabilized uncompacted fine-grained sulfide soil was used as cover mate-rial on a landfill. By-products from paper and cement industry were used as hydraulic binders. Samples were taken from the stabilized sulfidic fine-grained soil one year after the installation. Mainly geotechnical aspects as particle size distribution (PSD) and un-confined compressive strength (UCS) were investigated. In addition, the bu˙ering e˙ect of the binder was tested by pH measurements. Moreover, the mineral composition was investigated by X-ray di˙raction (XRD) and the micro-structure of some samples was investigated by Scanning Electron Microscopy (SEM). Parallel to the field study, samples were taken from the stabilized material directly after the installation of the field test. These samples were cured for one year in the laboratory under conditions comparable to those in the field. The testing program for these samples was similar to that for the field study.The main findings of this research can be summarized as follows:If fine-grained soil is mixed with the chosen by-products and compacted, the strength will increase compared to unstabilized soil even in cold environment and frost. The strength increase is slower in cold environment compared to reference values from literature for higher temperature.The chosen by-products bu˙er the potential acidification of the sulfide soil in cold en-vironment and frost. At the same time strength increase of stabilized sulfide soil in cold environment and frost can be achieved if compacted and protected against water percolation.

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  • 11.
    Abdullah, Twana
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Groundwater Vulnerability Assessment to pollution in Different Soil and Rock Materials2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The augmentation of human population regularly corresponds with change in the land cover, including expansion of urban areas, which imposes increasing the available amount of domestic and drinking water. The study area, Halabja-Saidsadiq Basin, is situated in the Northeast of Iraq and is one of the major groundwater sources of the region.  As the surface water sources are not enough in the studied area, it has become necessary to use groundwater at an increasing rate. Usually, a huge amount of groundwater is plentiful in the alluvial deposits or rock outcrops where the urban areas are frequently situated. Such areas face a huge risk of pollution of groundwater due to producing different sources of a contaminant from human's activity. Keeping these aspects in view, groundwater vulnerability studies have been carried out in the current studied basin. The main objective of this work is to investigate the environmental impacts on groundwater quality and recognize the groundwater vulnerability in the area so that the groundwater can be protected from probable contaminations.

    In the current study, DRASTIC model has been applied since it is one of the most proper useful methods available for the assessment of the groundwater vulnerability. This model has been modified in different ways to achieve the obvious vulnerability condition in the area; likewise, different further methods have been applied for comparison purposes such as: weight modified VLDA and standard COP models. In addition, the applied models were validated by comparing its findings against the estimated groundwater ages and the observed water characteristic qualities within the region in two successive seasons.

    According to the spatial distribution of irrigation water quality index, groundwater at the studied basin classified into three group for both dry and wet seasons, namely, Sever Restriction (SR), High Restriction (HR) and Moderate Restriction (MR). The coverage area of all three classes are (1.4%, 52.4% and46.2%) for dry season and (0.7%, 83.3% and16%) for wet seasons, respectively. While, refer to the water quality index for drinking purpose, groundwater in this basin reveals a permissible to excellent groundwater quality of the dry season and a good to excellent groundwater quality of the wet season. The high level of a good groundwater quality in the wet season compared to the dry season might be expected to the groundwater recharge during the winter and spring periods, which lead to dilution of chemical component, in contrast high irrigation and agricultural activities and groundwater discharge in the dry season leads to increase the concentration of chemical component.

    Field and official data were collected to review several environmental impacts and were used to map standard DRASTIC vulnerability model for the study basin. Based on this model, the study area was classified into four zones of vulnerability indexes, comprises a very low, low, moderate and high vulnerability index with a coverage area of (34%, 13%, 48% and 5%) respectively.

    In the first modification step, the rate and weight value of each parameter in DRASTIC model is modified. Nitrate concentration from 39 groundwater samples was used for modifying the recommended standard rating value based on the Wilcoxon rank-sum nonparametric statistical test and then sensitivity analysis was used to modifying recommended standard weighting value of each parameter. To calibrate the modified rate, the Pearson's correlation coefficient was applied to estimate the relation between DRASTIC values and nitrate concentrations in groundwater samples. For the first modified model, the correlation coefficient was 72% that was significantly higher than 43% achieved for the standard model. The modified model classified the area into five vulnerability classes, including (very low, low, moderate, high and very high) with covered area of (7%, 35%, 19%, 35% and 4%), respectively.

    The second modification of DRASTIC model was based on land use and land cover for the studied area. The land use and land cover (LULC) map prepared using ERDAS IMAGINE software from two different scenes of Landsat Thematic Mapper (TM). The LULC map indicates that only five classes of LULC can be identified: these are: barren land, agricultural land, vegetation land, urban area and wet land or water body. The modified DRASTIC based on LULC map classified the area into five classes with different coverage area of each class: very low (1.17%), low (36.82%), moderate (17.57%), high (43.42%) and very high (1.02%).

    The third modified method of the current study is the modification of DRASTIC model based on Lineament feature of the study basin. A lineament map is extracted from Enhanced Thematic Mapper plus (ETM+) satellite imagery using different techniques in remote sensing and GIS. The lineament density map demonstrates that only six classes of lineament density can be identified ranged from (0-2.4). The third modified DRASTIC model classified the area into four vulnerability categories: very low (28.75%), low (14.31%), moderate (46.91%) and high (10.03%).

    The fourth effort to modify standard DRASTIC model is the application of Analytical Hierarchical Process (AHP) to assess the weight value of each parameter. The modified DRASTIC vulnerability index values based on AHP method ranged between (65.82–224.1) with five vulnerability classes comprises (very low to very high).

    Weight modified VLDA and standard COP models were also applied to map vulnerability system in the study basin. The vulnerability outcome based on weight modified VLDA model revealed that a total of four ranges of vulnerability indexes had been distinguished ranging from low to very high with vulnerability indexes (2.133-9.16). Subsequently, based on the standard COP model, the area is also divided into four vulnerability classes ranging from very low to high with index value ranged from (0.79) to (6.2).

    All applied models in the study basin were compared to each other and validated to clarify the validity of the theoretical sympathetic of current hydrogeological conditions and to show the accuracy of the modeled vulnerability system. Two methods were applied for the validation of the result, in the first approach; nitrate concentration analysis has been selected; the nitrate differences between two following seasons (dry and wet) were analyzed from (39) water wells. In the second approach, groundwater vulnerability was assessed based on estimated groundwater age from range of tritium (3H) value in the groundwater samples from different groundwater aquifers in the studied area. The results of both validation methods verify the sensibility of the gradation and distribution of vulnerability levels acquired using the modified DRASTIC model based on (rate and weight modification, weight modification based on AHP process and effect of LULC on DRASTIC model) and also applying weight modified of VLDA model.

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  • 12.
    Ezz-Aldeen Mohammad, Mohammad
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sedimentation and Its Challenge for Sustainability of  Hydraulic Structures: A Case Study of Mosul Dam Pumping Station2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A successful management and operation of water resources projects are essential to maintain their functions. Dams and reservoirs are one of the largest worldwide infrastructures. They serve one or more functions; reliable store and release of water for different purposes, hydropower generation and   flood and draught controls. Sedimentation is one of the serious problems that affects the reservoir`s efficiency; it leads to reduction in storage capacity and reliability for water supply. Furthermore, deposition of sediment near and inside the intakes and hydropower plants cause a negative effect on plant efficiency and corrosion of turbines and pump`s impeller.    Generally, degradations of the watersheds, surface runoff and river flow are the main sources and transporters of the reservoir’s sediment.    Sediment management techniques are the most economical and efficient approach for sustainability of reservoirs and attached structures. Pumping rate, operation schedule, sub watersheds sediment control and earth dike is the reasonable alternatives that were applied in this study for sediment control and sustain water intakes.  In Mosul Dam reservoir, the pumping station is considered as a case study, the station is suffering from sediment accumulation in front and inside the intake. The work includes application of Soil and Water Assessment Tool (SWAT) models to estimate the runoff and sediment load delivered by sub watersheds surrounding the studied area, and a sediment rating curve was considered to assess the sediment load carried by the main river (Tigris River). The Hydrological Engineering Centre’s River Analysis System ( HEC-RAS) model   as a one dimensional model (1-D) was applied for sediment routing, and as a two dimensional model (2-D) for flow analysis. This aims to estimate the sediment load deposited in the studied reservoir and   evaluated the effects of pumping rate and flow depth on flow velocity distribution, flow stream power and sediment transport. As this study focuses on the sedimentation problem on the area around the intake’s structure and due to compound flow regime and sediment transport near the intakes and withdraws outlets, a three dimensional (3-D) model is considered more suitable than a 1-D or a 2-D model. The Sediment Simulation in Intakes with Multiblock option (SSIIM) model was considered also in this study; a proper control code for studied case was developed. This model depends on Computational Fluid Dynamics (CDF) techniques as a numerical method to solve fluid motion problems.

    The applied models were   calibrated and validated based on measured data of previous studies. The considered statistical criteria indicate that the models’ performances were reasonable for both flow and sediment assessments.  The results of all applied strategies show an improvement with a different percent in the amount of sediment deposited in front and inside of the intake, in comparison with the current situation. The optimal improvement was obtained by adding a control earth dike upstream the station. It is considered the most efficient and practical strategy that can be applied for sustainability of the   pumping station efficiency and lifespan with fewer dredging requirements.

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  • 13.
    Al-Jabban, Wathiq Jasim
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Soil Modification by adding small amounts of binders: A laboratory study2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Soil stabilization through addition of a hydraulic binder is a method frequently used to modify and improve engineering properties of soft soils. Additives like cement and lime are typically used as stabilizers. More recently, industrial by-products, such as fly ashes, cement kiln dust, blast furnace slags and other slags have been used. The chemical reaction between the soil and the stabilizer alters the physical and engineering properties of the soil and thus desired strength and durability are obtained. The choice of appropriate type and quantity of stabilizer (binder) depends largely on factors such as soil type, moisture content, organic content, sulfate content, curing conditions (time and temperature) and the desired improvement.

    The objective of this thesis is to increase knowledge and understanding of how small amounts of binders change various engineering properties of stabilized soils in short- and longtime perspective. Extensive laboratory and field programs have been carried out. They cover immediate and long-term effects on the engineering properties by adding various binders. Cement, Multicem, and by-products Petrit T and Mesa were used as binders. Binder was added to the soil at various quantities: 1%, 2%, 4%, 7% and 8% of soil dry weight. The field and laboratory investigation included tests of consistency limits, sieving and hydrometer, unconfined compressive strength, density, solidification, grain size distribution using laser particle size analyzer, leaching tests and pH value. The tests were carried out on the treated soil with different binder contents and after different curing times i.e. 7, 14, 28, 60, 90 days for laboratory tests and 7 and 35 days for field investigation.

    The unconfined compression tests were used to show the effects of different binders on the enhancement in strength and stiffness over time. Consistency limits were determined to investigate the effects of the binders on the consistency limits, directly after treatment and over time. Laser particle size analyzer tests were conducted to investigate the effects of different binders on the particle size distribution (PSD) before and after treatment. The pH tests were conducted to investigate the effects of different binders on the alkalinity of the soil immediately after treatment and over time. This was used to give an indication of soil-binder reactions. MRM leaching tests were conducted to investigate the acidification potential of soils before and after treatment. Freeze-thaw cycles were conducted to investigate the strength characteristics after freezing and thawing in short- and long-term perspectives. Visual observation and standard dry sieving tests were conducted to optimize the proper mixing times to disintegrate or homogenize the soils by decreasing the size of agglomerated soil particles.

    The results show, that the variation in soil strength and stiffness of the treated soils are linked to different chemical reactions. Cement is most effective in improving the physical and engineering properties compared to the other binders studied. The plasticity index of soil decreases after treatment and over time. Liquidity index and the ratio of water content to plastic limit are introduced as new indices to illustrate the improvement in workability of treated soil by measuring the reduction in the liquidity index. This is found directly after treatment and it increases with time when the liquidity index is within the plastic range or when the water/plastic vi limit ratio is more than one. Increase of binder content and using longer curing times result in increase of soil density and decrease of water content. Particle size distribution of soil is changed by reducing the clay size fraction and increasing the silt size particles after treatment. This shows that an aggregation of particles take place resulting in coarser material than the initial. The cement-treated soils exhibit a more brittle failure in the unconfined compression tests compared to soils treated with other binder types where a more ductile behavior is observed. Applying freezing-thawing-cycles reduces the strength and stiffness of the treated soil.

    The appropriate length of time to homogenize and disintegrate the natural soil prior to treatment depends on several factors, such as soil type, water content, and plasticity properties of soil. For high plasticity soil, the disintegration time should be kept as short as possible. The homogenizing and disintegration time is less important for low plasticity soils with low water content than for medium to high plasticity soils.

    The acidification potential of soils are related to the addition of cementitious binders. The effect is found directly after treatment and over time. The treated soil exhibits higher resistance to decrease in pH value. The strength and stiffness properties found in the field investigation agree in general with those obtained from the laboratory investigation for the same binder type.

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  • 14.
    Chabuk, Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Solid Waste Landfills in an Arid Environment : Site Selection and Design2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Selecting landfill sites is considered a complicated task because its whole process is based upon several factors and restrictions. This study shows the present status of solid waste management, sources, collection personnel, machinery and equipment that are involved in the waste collection process, financing and financial management for the major cities of the Babylon Governorate in Iraq (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab). The management of waste collection and disposal in the Babylon Governorate and its districts is through open waste dumps, so the quality of the collection and disposal process is poor, and these sites do not conform to the scientific and environmental criteria usually applied in the selection of landfill sites.

    In the first part of the current study, three methods were used to calculate the solid waste quantity for each specific year up to the year 2030 as well as the cumulative quantity of solid waste for the period (2020-2030) for Babylon Governorate. The results show the cumulative quantity of solid waste resulting from (method 3) receives a high value compared to other methods, and so it is used as a maximum value to estimate the required area for candidate sites for landfills in each district. The generation rate in 2030 will be (0.97, 0.69, 0.48, 0.62 and 0.91) (kg/capita/day) in (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab), respectively, based on method 3, where the estimated annual incremental generation rate is 1 %. 

    The second part of this study aims to find the best sites for landfills in the arid areas that are distinguished by a shallow depth of groundwater. The Babylon Governorate was selected as a case study because it is located in an arid area, and the depths beneath the ground surface to the groundwater level are shallow.  

    For this purpose, 15 important criteria were adopted as follows: groundwater depth, rivers, soil types, agricultural land use, land use, elevation, slope, gas pipelines, oil pipelines, power lines, roads, railways, urban centers, villages and archaeological sites. These criteria were then entered into the geographic information system (GIS). The GIS software has a large capacity to manage and analyze various input data using special analysis tools. In addition, Multi-Criteria Decision Making (MCDM) methods were used to derive the relative weightings for each criterion in different styles. These methods are (Analytical Hierarchy Process (AHP), Simple Additive Weighting (SAW), Ratio Scale Weighting (RSW) and Straight Rank Sum (SRS)).

    Raster maps of the selected criteria were prepared and analyzed within the GIS software. The final map for candidate landfill sites was obtained through combining the GIS software and (MCDM) methods. Subsequently, comparison methods (Change Detection, Combination, Kappa and Overall Assessment) for each pair of raster maps that result from using the two different methods of multi-criteria decision making were implemented to determine the pixel percentage of matching and non-matching as well as to determine and check the suitability of the selected sites for landfills on both resulting maps using two methods.  

    Two suitable candidate sites for landfills were determined to fulfill the scientific and environmental requirements in each major city. These areas are (6.768 and 8.204) km2 in Al-Hillah, (2.766 and 2.055) km2 in Al-Qasim, (1.288 and 1.374) km2 in Al-Hashimiyah, (2.950 and 2.218) km2 in Al-Mahawil, and (7.965 and 5.952) km2 in Al-Musayiab. The required area of the selected sites can accommodate solid waste from 2020 until 2030 based on the required areas according to the third method.

    The third part of this study includes soil investigations for the selected landfill sites. The suggested design should ensure that there is no groundwater pollution by leachate from these sites because the groundwater depth is very shallow in the Babylon Governorate. To avoid this problem, soil investigation was conducted at these sites so that the most suitable landfill design could be established. Each site was subjected to field soil tests to find the composition of the soil strata at each site to a depth of 10 m, and these results were compared with the soil properties adopted for final site selection. The Iraqi Ministry of Housing & Construction, National Centre for Construction Laboratories and Research Babylon, Iraq, carried out the analytical work on the soil in 2016. The results of the soil investigation at these sites include the soil profile, groundwater depth, chemical properties, allowable bearing capacity, atterberg limits test results and material characteristics of the soil strata. According to the results of these tests, the best design is the one that puts the compacted waste at the surface.

    The fourth part of this study covers the selection of a suitable proposed design in the arid areas (Babylon Governorate, Iraq) for the selected landfill siting. In the current study, the design of this landfill includes the suggested soil layers for the liner system and final cover system.  

    For the base liner system (from the bottom toward the top), the composite bottom barrier layer consists of highly compacted sandy clay. The thickness of the bottom barrier layer is 60 cm, and its saturated hydraulic conductivity is 1.0E-7cm/s. The 1.5 mm thick geomembrane (HDPE), with hydraulic conductivity of 2.0E-13 cm/s, is placed over the composite bottom barrier layer. The leachate collection system consists of drainage layer (gravel) with a thickness of 30 cm and a hydraulic conductivity of 3.0E-1 cm/s. The diameter of the main drainpipes is between 15 and 20 cm. The protection layer consists of sand material, and its hydraulic conductivity is 5.0E-3 cm/s. The thickness of the protection layer is 30 cm.

    The compacted solid waste is placed upon the surface to a height of 2 m because of the shallow groundwater depth and to avoid groundwater contamination by leachate from the landfill site. The density of the compacted waste is 700 kg/m3, and its saturated hydraulic conductivity is 1.0E-5 cm/s.

    Three scenarios were used for the suggested designs for the final cover system of the landfills in arid areas. The first scenario was “evapotranspiration soil cover (ET) (capillary barriers type)”, the second scenario was a modified cover design of "RCRA Subtitle D", and the third scenario was the “Recommended design”. In this study, “Recommended design”, the third scenario for the final cover system, was adopted in the arid area (Babylon governorate, Iraq) based on combining certain layers from the first and second scenarios. For the three scenarios, the soil components in these designs used was based on available local materials in the study area. The layers of the base liner system were adopted in all scenarios.

    The third scenario for the final cover system, “Recommended design”, was implemented based on weather parameters in the arid areas. The water infiltrated from the surface of landfill is stored within upper layers that have fine particles. This allows the stored water to evaporate from the soil surface of the landfill or transpire through vegetation due to the high temperature during most months in the study area. The water that enters from the surface of the landfill should be contained above the geomembrane liner and top barrier layer without leakage into the waste body, thereby preventing leachate generation.

    For the layers of the final cover system (from the bottom to the top), the intermediate cover is used to cover the waste body, and this layer consists of moderate compacted silty clayey loam (native soil). The thickness of the intermediate cover is 30 cm, and its saturated hydraulic conductivity is1.0E-6 cm/s. The foundation layer consists of coarse sand material with a thickness of 30 cm and a saturated hydraulic conductivity of 1.0E-2 cm/s. This layer acts as a cushion for the layers of the final cover system. The gas collection system can be installed within the foundation layer.  

    The top barrier layer is placed over the foundation layer. This layer consists of highly compacted sandy clay of (45 - 60 cm) thickness with compacted lifts (each lift is 15 cm). The saturated hydraulic conductivity of the barrier layer is 1.0E-7 cm/s. The geomembrane liner, (HDPE) of 0.5 cm thickness and a saturated hydraulic conductivity of 2.0E-13 cm/s, is put on top of the barrier layer. The upper layers of the final cover system are the support vegetation layer and the topsoil layer. The composition of the support vegetation layer is moderate compacted loam. This layer is placed directly on the geomembrane liner. The saturated hydraulic conductivity of the support layer is1.0E-5 cm/s, and its thickness is 45 cm. The topsoil layer consists of silty clayey loam, and it is placed over the support vegetation layer with a slope of 3%. The thickness of the topsoil layer is 15 cm, and its hydraulic conductivity is 4.0E-5 cm/s.  

    The Hydrologic Evaluation of a Landfill Performance (HELP 3.95 D) model was applied to the selected landfill sites in the governorate to check if there could be any infiltration of the leachate that will result from the waste in the landfills in the selected sites in the future. The HELP model, which utilizes both weather and soil data, is the most commonly used model for landfill design, and it is employed to evaluate the quantity of water inflow through soil layers for the designed landfill. This suggested landfill is designed using the weather parameters (rainfall, temperature, solar, and the required date to calculate evapotranspiration) for the 12 consecutive years from 2005 to 2016, as well the required data for soil design.

    In the HELP model, the result for the suggested landfill design for both the recommended design (third scenario) and the second scenario was a modified cover design of "RCRA Subtitle D", which showed there was no leachate through the soil sub-layers, including the bottom barrier layer. The proposed design for the final cover system showed a reduction in the surface runoff and an increase in actual evapotranspiration. In the first scenario “evapotranspiration soil cover (ET) (capillary barriers type)”, there was no leachate percolation through the bottom barrier layer during the study years, apart from in 2013 and 2014. In these years, water percolation figures were 1.4E-5 and 4.0E-6 mm, respectively. These values are considered small, and they resulted from the high rate of rainfall during these years. Although, these values were small, they should still be taken into consideration when adopting this design in the study area.

    In the HELP model, the average annual and peak daily results for all scenarios showed that there was no water percolation through the bottom barrier layer during the years from 2005 to 2016.

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  • 15.
    Knutsson, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    On the behaviour of tailings dams: Management in cold regions2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Associated to mining activities there is mine waste generated. The residues left over from mineralextraction processes are referred to as tailings, normally stored in surface tailings facilities. Thefacilities are usually confined by embankment dams, so called tailings dams. Sufficient stability of thetailings dams is essential, and a proper management of the tailings is needed in order to maintain asafe storage. However, optimal strategies for tailings management are very much site specific, andthere is no universal answer on how tailings management should be applied. Despite the availableguidelines, recommendations and current trends in the industry on how to handle tailings, theremust be a pertinent approach to optimize tailings management to the site-specific conditions.

    The aim with the work presented in this thesis is to enhance current practice in tailings managementin cold regions. Three sets of research objectives are presented, from which recommendations will begiven on how management can be adjusted for site-specific conditions.

    Firstly, depositional aspects in cold climate are studied. A methodology is proposed where thethermal regime is studied in a tailings facility with active deposition, i.e. raised tailings surface, andconcurrent freezing and thawing. Despite the fact that there is no natural permafrost in Sweden, thedeposition can imply generation of “man-made” permafrost in the facilities. The model is simple andeasily accessible data are used as input. With a proposed methodology, deposition schedules can bemodelled, and the deposition scheme can be adjusted in order to prevent permafrost generation intailings facilities.

    In addition to the depositional aspects in cold climate, a study is presented focusing on thaw stabilityof tailings beach slopes. The tailings beach is the inclined surface of settled tailings without pondedwater. For conventional tailings deposition, the beach slopes are relatively flat and the need for thawstability analyses is trivial. However, there is a current trend of adopting thickened tailingstechnology where steeper beach slopes are one of the intended merits. The increased slopeinclination might be unstable with major seasonal freezing and thawing. In rapid thaw excess porewater pressure might be generated, creating instability where masses of tailings can slide along a stillfrozen interface. Increased storage capacity, or freeboard, along the surrounding dams might beneeded, and the intended merits with the thickened tailings technology might be lost.

    Secondly, a study on the determination of strength parameters on granular soil is presented. Simpleshear tests are widely used particularly in Sweden for soil strength determination. However, recentstudies on tailings indicate large differences on the evaluated strength compared to what isdetermined via triaxial testing. In this thesis a laboratory study is presented, where simple sheartesting and triaxial testing were conducted. The results were used for examining the Swedishguidelines on simple shear testing and associated strength determination. It was found that directapplication of strength determined by simple shear testing leads to incorrect design assumptions.

    Thirdly, a study on prediction and verification of tailings dam stability is presented. Dam stability iscentral in tailings management, and a convenient way to describe the safety is via the factor of safety(FoS). Although the FoS can be predicted via calculations, it cannot be measured directly in the field.Therefore, in order to verify the calculated stability, field measurements must be used to comparewith the anticipated performance. With good agreement the prediction indicate reliableunderstanding of the dam, and the predicted stability can be verified. Without good agreement, thestability is easily questioned.

    Based on findings from the three sections presented in the thesis, recommendations are given ontailings management in cold regions. With increased knowledge in the field of tailings deposition incold climate, shear parameter determination and overall dam stability assessment, current practice intailings management is enhanced.

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  • 16.
    Yang, Ting
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Maturation of Clay Seals in Deep Bore Holes for Disposal of Radioactive waste: Theory and Experiments2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    KBS-3 and very deep borehole (VDH) concepts are two major types of long-term geologicaldisposal methods for high-level radioactive waste (HLW) isolating from the biosphere. TheKBS-3V concept for isolating the HLW at the depth of 400-500 m, is the officially proposedoption in Sweden and has been the subject of considerable research in the past few decades,while the VDH concept was considered as an option in the 1950s but later became discouragedbecause of insufficient experience in drilling technology. The greatest merit of the VDHconcept is that the almost stagnant groundwater in the deep boreholes prevents the transport ofthe possible release of radionuclides into the rock or up to the ground level. Since variousdisadvantages of the KBS-3V concept were found in previous research, the superiority of VDHconcept attracted the researchers to continue studying it into the late 1980s.The geological repositories of both of KBS-3V and VDH types primarily consist of a naturalbarrier (host rock) and of an engineering barrier (also known as a buffer/backfill barrier).According to the principle of IAEA and national relative research organizations, thebuffer/backfill material should have low permeability and good expandability, as well assuitable physical and sealing properties.The thesis concerns the VDH concept and is focused on the construction and performance ofthose parts of the sealed repository that are not affected by high temperature or gamma radiation.In the lower part of a VDH repository, the clay packages containing HLW will be exposed tohigh temperature (100-150 􀄇 ) in the borehole and to highly saline groundwater. In theinstallation phase of HLW, the groundwater will be pumped out and replaced by medium-softsmectite clay mud in which the HLW packages are installed vertically. During the hydrationand maturation of the clay components, the microstructural reorganization, water transport,migration of clay particles and redistribution of the density of the components take place. Thematuration determines the transient evolution of the clay seals and influences the rheologicaland soil mechanical behavior in the installation phase. The maturation of clay system alsodetermines their ultimate sealing potential of VDH repositories.This study presents the work carried out for investigating the maturation of the buffer-backfillclay in the HLW deep borehole. Initially in the study three types of clays, the Namontmorillonite,magnesium-rich and illite-smectite mixed layer clays, were examined for estimating their performance as the barrier candidate material. This is mainly presented in theliterature review. The experimental study was conducted on montmorillonite GMZ clays andI/S mixed-layer Holmehus clay. The expandability and permeability tests were carried out forinterpretation of the recorded swelling development and assessment of the effect of the salineconditions, with the goal of deriving a relationship between swelling pressure and hydraulicconductivity for different dry densities. The maturation tests of initially fully-saturatedHolmehus clay and partly saturated GMZ clay were performed. During the tests, the shearstrength mobilised by the relative movement of densified mud and migrated dense clay -contained in a perforated central tube - were determined. According to the results of shearstrength tests, the maximum operation time or the number of clay packages to be placed in asingle operation was evaluated, whilst the suitable saturation degree of the dense clay wasdiscussed as well.A model of the maturation of initially water-saturated clay seals based on Darcy’s law wasworked out and the evolution of the clay components in a lab-scale borehole using Holmehusclay were performed and compared with the experimental recordings. Good agreementsbetween the physical behaviors of the theoretical simulations and the measurements wasachieved by which the validity of the model was verified. Using the results, the hydration andsoil migration in the entire maturation process were presented in diagram. The model was alsoused for preliminary evaluation of the maturation products in real boreholes by assuming thesame Holmehus clay as used in the tests. Two constellation of borehole and dense clay withdifferent diameters, 80 cm borehole /60 cm clay and 80cm/50cm, were assumed. The resultsrespecting dry density and hydraulic conductivity of the ultimate maturation products, and thedegree of homogeneous of the buffer and backfill clay system in the assumed boreholes, arepresented and discussed. The options of different mineral types and initial physical propertiesof the candidate buffer clays provide a reference for engineering barrier design of HLW disposalin VDH.

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  • 17.
    Bhanbhro, Riaz
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mechanical Behavior of Tailings: Laboratory Tests from a Swedish Tailings Dam2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tailings is leftover material from mining industry and is produced in huge quantities approximately 70-99% of the ore production.  Tailings material is stored as impoundments by constructing tailings dams which are often constructed with tailings material itself. Tailings are artificial material and the mechanical behavior of tailings material upon loading is different as compared to natural soil materials. There are number of dam failures reported every year which has severe impact on inhabitants and environment nearby. Considering the failures of tailings dams and consequences there is a need to understand the tailings material in depth for safe existence of these dams. The confident dam design can assure the safe existence of tailings dams for long term as these dams are presumed to function for generations to come. The material properties in tailings dams can change during operation due to raising of new layer. Raised new layer can change stress level, which in turn may change the material properties in terms of strength, pore pressures, grain sizes etc. Today mostly tailings dam are designed by performing analysis for safety for existing and future rasings as well. These analyses are based upon a for certain factor of safety. Not very much can be done with design and analysis for tailings material if the material is not described very well. Understanding of tailings material in depth can provide help for detailed material parameters which later can be used in safety assessment for future raising and changed conditions in dam.

    This study presents the work carried out on tailings material from a Swedish tailings dam. The study is conducted on undisturbed and disturbed tailings material. The undisturbed tests are carried out to understand material properties as per in-situ conditions. Whereas disturbed materials are used to created different materials with different particles sizes. Initially in this study the basic properties of tailings materials are studied e.g. specific gravity, phase relationships, particle sizes, particle shapes and shear behavior on collected samples at various depths. During direct shear tests, the unexpected vertical height reductions were observed, these results are presented in this study. The comparison of strength parameters by direct shear and triaxial tests on material from various depths is also done and presented.

    Based on results from direct shear, triaxial and oedometer tests on uniform sized tailings material; the evaluation of primary and secondary deformations and particle breakage and effect of vertical loads is also carried out and presented. The study also includes the comparison of strength parameters for each particles size. The breakage of particles is analyzed by sieving the material after direct shear tests followed by a particle shape study. The effect of deposition on shear strength parameters is also studied by construction of samples with different angle of deposition of material. The strength parameters of uniform sized particles in triaxial tests are also evaluated and discussed.

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  • 18.
    Altaie, Entidhar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Analysis of Shallow Foundations in Three Different Regions in Iraq2016Doctoral thesis, comprehensive summary (Other academic)
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  • 19.
    Rodriguez, Juan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of Physical Weathering on Mechanical Properties of Tailings2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mining activity produces minerals to supply to the modern society with commodities. During the ore refining process large amounts of tailings are generated as waste. Tailings are the result of crushing and wet milling, typically in the size range of sand to silt and angular in shape. Tailings are in general deposited in tailings dams for permanent storage. Tailings dams are usually considered as walk-away solutions and needs to be designed and constructed to be safe in a long time perspective. Several incidents around the world have occurred in tailings dams both during construction and operation and after closure of the activities. The consequences of the failures may be fatal to the local society and harm the surrounding environment. Considering the consequences of failures and relatively few studies on tailings properties in a long term perspective there is a need for research. As a consequence of the operation and raising procedures of tailings dams, the conditions in the tailings dams could be considered to be dynamic in a longer perspective. Grain size distribution, formation of layers, pore pressures and stress states are continuously changing during the operation. Tailings may be susceptible to weathering in the deposit environment. The change of these factors needs to be addressed in the design of walk-away solutions. In this work image analysis, oedometer-, triaxial-, direct shear- and attrition tests has been carried out to study the tailings particle influence on fundamental geotechnical properties in a case study. The parameters have been compared to similar-sized natural materials. The effect of loading and physical weathering has been studied and evaluated by image analysis and sieving. The comparative test by natural materials shows that tailings, probably due to the irregular shape, initially arranges in looser interparticle structures. The looser arrangement makes tailings fills more susceptible to settlement compared to natural deposits in the same size range. The two most identified factors affecting the tailings on a particle level was the type of physical weathering and grain size. Static load, shearing and milling decreases the grain size but the effect on the individual particles were different. Large grains tend to maintain the shape or get rounded by physical degradation and finer grains get more angular by milling but rounded by shearing. An attempt has been done to predict the effect on friction angle as a function of angularity, grain size and initial void ratio. The increase in angularity in the model suggests an increase in the friction angle and so the increase of regularity (decrease of elongation relation). However the reduction of size will either reduces or compensates this effect. More studies are needed to verify this.

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  • 20.
    Lintzén, Nina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Properties of snow with applications related to climate change and skiing2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Snow has been a subject of research since the mid-20th century. Research on mechanical properties of snow started as an off-shoot of soil mechanics, where methods, tools and instruments used often are the same. However, during the last decades the winter business industry has been growing requiring a number of new fields of research. The aim with this PhD thesis is to investigate and contribute to solutions of some of the new research problems appearing in this area. Machine-made snow is commonly used for buildings and artwork of snow. Only minor scientific studies of machine-made snow and its properties have been published. Therefore, mechanical properties of machine-made snow were investigated. Strength and deformation properties were evaluated through uniaxial compressive tests where cylindrical test specimens were subjected to different constant deformation rates. Creep deformation, bending strength and ultimate load were also evaluated through beam tests. The results showed that the deformation rate is crucial if the snow will deform plastically or if brittle failure will occur. The grain size and structure of the snow had a strong influence on the strength properties. Snow is a constantly changing material with a large variety of grain sizes and shapes. Therefore it is of importance to classify snow. Classication of snow can be done using different methods depending on the property that is to be investigated. Several non-contact detection methods to evaluate snow properties exist. In this thesis, spectral reflectance measurements were performed to investigate liquid water content in snow using two different systems, a spectrometer and an optical sensor called Road Eye. The Road Eye sensor was also used to classify snow in cross-country ski tracks. This method enables a fast classication of a complete track where different types of snow can be distinguished. The properties of a ski track and the characteristics of the snow determine the type of skis that should be selected for optimum sliding properties. Cross-country skis have different mechanical properties, which to a large extent can be evaluated from the span curve of the ski. Depending on the skiing style, the skier's skills, terrain and track conditions different ski properties are required, which is particularly important for competitive skiing. Span curves of cross-country skis were measured using a digital instrument called Skiselector. Results from the investigations showed that skis within the same pair may have signicantly different properties. Moreover, temperature influences the span curve and thus the mechanical properties of the skis. Therefore, skis should be measured at a temperature close to where they are aimed to be used. Field tests of skis with similar span curves but different ski base topography were tested during wet and cold snow conditions. The results indicate that different topographies are preferable during different snow conditions. Due to the climate change, winters have become shorter and warmer with less natural snow. To compensate for the lack of natural snow, ski resorts and other stakeholders produce machinemade snow in order to run their business. Storing snow in insulated piles is an alternative and sometimes a complement to snow production. Studies on stored snow show that the surface area of the pile should be minimized in order to reduce the melt rate. Furthermore, the pileshould be covered with a suciently thick insulating layer, preferably with good evaporation properties. Theoretical calculations can be used to estimate the amount of snow that melts and to predict the efficiency of different materials as thermal insulation on snow. These calculations coincide well with experiments performed in northern Sweden where snow melt was measured. This PhD thesis consists of five publications and an introduction to this area which in particular puts these publications into a more general frame.

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  • 21.
    Ali, Ammar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Three Dimensional Hydro-Morphological Modeling of Tigris River2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The River Tigris is a major river in Iraq. It divides Baghdad, the capital of Iraq, in two parts. The reach of the river within Baghdad is about 60 km long. The climate change within the region and the construction of hydraulic structures upstream of Baghdad has reduced the water discharge of the river by 44%. Despite the fact that huge volumes of sediment have been trapped in the constructed headwater reservoirs, substantial changes have occurred in the topography of the Tigris River within Baghdad City and the number of depositions is increasing. The debris of the destroyed bridges from the wars of 1991 and 2003 and their subsequent reconstruction have contributed to the development of these depositions. As a consequence, the ability of the river to carry the peak flood waters has been reduced. This has led to a potential increase of flooding in parts of the city. To predict the maximum flood capacity for the river, the bathymetric survey that was conducted for 50 km of the Tigris River by the Ministry of Water Resources in 2008 has been used with the one-dimensional flow model “HEC-RAS”. Calibration of the model was carried out using field measurements for water levels along the last 15 km of the reach, and the water level observations at the Sarai Baghdad gauging station for the last 10 years were used to validate the model. The model showed a significant reduction in the river’s capacity compared with what the river had carried during the floods of 1971 and 1988. This result agrees with previous surveys conducted on the same reach indicating that the ability of the river to convey high water has decreased. To overcome this problem, dredging operations started along most of the Tigris River inside Baghdad City to remove many islands and side bars, as well as cleaning water intakes. An examination for the dredging plan currently in progress and two additional proposed plans was conducted using the ‘HEC-RAS’ model for the 50 km long river reach to investigate whether the designed flooding capacity of the river can be recovered and how much it can be improved. Comparing the historical records of water level and discharge for the last three decades, some improvement of flood capacity was achieved. Cautions about the water intakes should be considered to maintain their functionalities with the expected drop in water levels due to dredging operations. Bathymetric and land surveys were conducted for the northern Tigris River reach (18 km length) in Baghdad, producing 180 cross sections. A riverbed topography map was established from these cross sections. Sediment transport rates and bed composition were investigated by collecting three different types of sediment samples at the quartiles of 16 cross sections along this reach. The Helley-Smith sampler was used to collect 288 bedload samples, a suction pump was used to collect 212 suspended load samples from different depths. The Van Veen grab was used to collect 46 bed material samples. The velocity profiles and the water discharges were measured using ADCP at the sampling sections. Bed sediment compositions were investigated by analysing the collected bed material samples. It was noticed that fine sand dominated the riverbed (90.74%). The average median size within the reach was 2.49 phi (0.177mm) whilst the mean size was 2.58 phi (0.16mm). In addition, the sediments were moderately sorted, fine skewed and leptokurtic. The size of the bed sediment relatively decreased compared to older investigations due to the decrease of the competence of the river. The bed elevation had increased compared to previous surveys. It was noticed that dredging operations and obstacles (e.g. fallen bridges and islands) disturbed the flow of the river and the sediment characteristics in several sites. Bedload rates were computed using the weights of the collected bedload samples. The spatial distribution of sampling cross sections took into consideration the variance of river topography where 7 meanders, 2 islands and several bank depositions characterize the geometry of the river reach. Twenty bedload predictors were applied to the same reach. The annual transported quantities of the bedload were estimated to be 36 and 50 thousand tons in 2009 and 2013 respectively. The total load discharge rate in the northern reach of the Tigris River was computed using the sediment concentrations of the collected suspended load samples after adding the bedload rate at each of the sampling cross sections. The results indicated that the suspended load is the dominant mode in the total load with a minimum percentage of 93.5%. The total load ranged from 29.1 to 190.3 kg/s. A total load rating curve of the power function was established. The associated errors from using the proposed rating curve are within reassuring levels and less than the errors produced from most of the other twenty-two total load formulas, which were applied to the same reach. The scattering of the results from the other formulas can be attributed to the spatial variance in the topography of the riverbed. According to the final results obtained, it is recommended to use the proposed procedure for establishing a spatial total load rating curve to estimate sediment rates for morphologically complicated rivers. The annual transported quantities of the total load were estimated at 2.47 and 4.23 million tons for 2009 and 2013 respectively. The three-dimensional morphodynamic model (Simulation of Sediment movements In water Intakes with Multiblock option - SSIIM) was used to simulate the velocity field and the water surface profile along the northern reach of the Tigris River using the findings of the current bathymetric survey of the river. The model was calibrated for the water levels, the velocity profiles and the sediment concentration profiles using different combinations of parameters and algorithms, those available in the model. The set of parameters that gave a minimum root mean square error (RMSE) was used for the validation process using another set of field measurements. The calibration and the validation results showed good agreement with field measurements, and the model was used to predict the future changes in river hydro-morphology for a period of 14 months. The results of the future predictions showed increases in depositions on the shallow part of the cross section having lower velocity and, on the other hand, the river deepens the incised route to fit its current hydrologic condition leaving the former wide section as a floodplain for the newer river. The net deposition/erosion rate was 67.44 kg/s in average and the total deposition quantity was 2.12 million tons annually. The locations of depositions are compatible with those of the river in the real world. An expansion in the size of current islands was predicted. An indication of the potential threats of the river banks’ collapse and the bridge piers’ instability was given by high erosion along the thalweg line.Keywords: Flood capacity, Dredging, HEC-RAS, Bathymetric survey, Bed sediment, Bedload, Total load, Helley-Smith sampler, Sediment transport, ADCP, Prediction formulas, 3-D morphodynamic model, Bed changes, SSIIM, underfit river, regulated river, Tigris River, Baghdad.

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  • 22.
    Jia, Qi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Estimation of industrial dust using exposure-profiling method2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dust is a primary cause for air quality deterioration, as well as a potential health hazard. Mining and construction sites, in particular, are the most profound in dust generation. The possible source activities are drilling, loading, transporting, dumping, crushing, stockpiles, waste rock and unprotected open surfaces, etc. Dust can be any airborne contaminants occur in the gaseous form or as aerosols. This research dealt with ‘fugitive dust’ which is defined as dust that could not reasonably pass through a stack, chimney, vent, or other functionally equivalent openings, and does not include non-geologic particulate matter emitted directly by internal and external combustion processes. Fugitive dust and dust are used interchangeably in this thesis.In mining areas, construction sites or other industrial areas, fugitive dust is generated through wind erosion of surface materials or application of mechanical forces. The transportation of dust particles is a result of wind direction, velocity, source activities, particles dispersion characteristics, topography, control methods, and so on. A case study on dust fallout from Malmberget Iron Mine showed that the dust generation due to the mining activities in Malmberget Iron Mine influences the down-wind residential areas depending on the weather conditions and the rate of dust generation; the sources of dust generation from Malmberget Iron Mine are haul road transportations, active stockpiles, and the open pit with the loose surface materials. Dust due to wind erosion of the loose material from the open pit is somewhat insignificant as the lab tests showed that the surface material was slightly to moderately erodible and has the soil erosion index of 4.7kg/m2/year.To measure dust generation, three sites were used. They are unpaved roads, road construction and the Aitik tailings dam. This was achieved using an exposure-profiling method with Big Spring Number Eight (BSNE) samplers. Wind erosion prediction system (WEPS) was also used to model the wind erosion process on the Aitik tailings dam. The measurement for the unpaved roads showed that dust generation strongly depends on the driving speed and silt content of road surface materials when the moisture contents are the same. The estimated dust emission rate from the road construction work during the measuring period was 22.87 kg TSP/d, of which 6 kg/d was from construction work and 16.87 kg/d was generated due to traffic on temporary roads. The measured total suspended material from the Aitik tailings dam was 0.475kg/m2 for five days, which had a big difference with simulated value of 4.4559 kg/m2. Many reasons contributed to the disagreement between the simulated value and the measured value. In order to use the model for mining industry more tests are required to validate the modeling result. This could be useful in adjusting the internal coefficients and empirical equations.The research concluded that the exposure-profiling method with BSNEs worked best for the unpaved roads which is a line source, whereas for the road construction and the Aitik tailings dam the method was not robust enough. BSNE sampler is cheap and widely used, but can produce poor accuracy in some cases. Upwind-downwind method with active samplers is recommended for the road construction and the tailings dam which are the non-line sources in the future work. Both of the methods are applicable for development of dust emission factors. WESP is a soil erosion model designed for agriculture land and need to be validated with more field tests in order to be used for the tailings dam.

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  • 23.
    Rönnqvist, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    On the Assessment of Internal Erosion of Dam Cores of Glacial Till2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objective of this study is twofold; on the one hand it investigates the susceptibility to suffusion of glacial till, and, on the other, it presents approaches to evaluate internal erosion susceptibility of dams composed of this type of core soil. Concentrated leak erosion, backward erosion, contact erosion, and suffusion erosion are the mechanisms associated with the initiation of internal erosion. How these interplay in the continuation phase is still a relatively unresolved issue. In engineering practice, these mechanisms have all been seen in dams with glacial till cores; backward erosion activity as seen in Juktan dam, Juklavatn dam, Grundsjöndam, Wreck Cove dam, and in Brodhead dam; possible suffusion as seen in Lövön dam and in Stenkullafors dam; and, furthermore, signs indicating concentrated leaks, such as in Songa dam. A laboratory program of tests was performed on four natural, non-plastic glacial till soils from the core or its borrow area of existing earth dams in Sweden, and on eight mixtures based on these tills, making in total 12 tests. The longest running for 77 days, and the highest applied gradient was 9.5, in bounds of what can occur in dam cores. The tests revealed that gradations of low fines content (< §15–20%), low sand fraction (< §20%), and high gravel fraction (> §60%) are susceptible to suffusion. These are grading characteristics present in the coarse end of the envelope of glacial till cores in many existing dams. Available state-of-the-art assessment criteria for internal stability were evaluated in reference to these experimental data, yielding a modification to the Kenney-Lau adaptation by Li-Fannin. Furthermore, a screening tool for the assessment of internal erosion of dams is proposed, i.e., the unified-plot approach, which combines attributes of the filter gradation and the probable occurrence of internal erosion in a dam. Given the variety of potential mechanism interplaying in the internal erosion of dams with cores of glacial till, it lend confidence to an assessment approach which addresses, susceptibility to several mechanisms.

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  • 24.
    Issa, Issa E
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sedimentological and Hydrological Investigation of Mosul Dam Reservoir2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reservoir sedimentation is the main problem that directly affects the performance of dams due to the reduction in the storage capacity of their reservoirs. Monitoring the storage capacity of reservoirs is an important issue for the planners, designers and operators of the dams. Iraq mainly depends on the rivers Tigris and Euphrates for its water resources. Until the 1970s, Iraq was regarded as a rich country with regard to its water resources, due to the presence of the Tigris and Euphrates rivers. Recently, its water resources have decreased significantly due to an increased water demand and global climate changes. In view of this situation, it became necessary to know about Iraq’s water resource trends to adopt prudent water resource management strategies. Among these strategies is the assessment of the sedimentation rates in its reservoirs to determine their actual storage capacities and reduction rates of storage capacity through time. Mosul Dam Reservoir (MDR) is the biggest and one of the most important strategic projects in Iraq. It is a multipurpose project constructed to store water and to handle flood control and hydropower generation but the main purpose was to provide water for three irrigation projects that cover 2,500 km2 of agricultural areas. The dam is located on the River Tigris in northern Iraq, 60 km north-west of the city of Mosul. The project was designed to store 11.11 km3 with water surface area of about 380 km2 at the maximum operation level 330 m a.s.l. It is noteworthy to mention that MDR has operated since 1986, and no detailed studies have been carried out to determine the sedimentation characteristics in its reservoir since that time. In the present work, the storage capacity, sedimentation rates, area-storage capacity (ASC) curves, sediment nature and their grain size distribution and bottom morphology of its reservoir were studied. Direct and indirect methods were used to achieve these goals. In the direct methods, two topographic maps for MDR’s area were established in a triangular irregular network (TIN) format using Arc/GIS software. One of them before dam construction from pre-construction topographic map scale 1:50000 and other from bathymetric survey that was conducted in 2011. These maps were used; to calculate the volume of deposited sediment, to develop and evaluate ASC curves, to determine the bed morphology and to estimate the useful life of MDR. The results of the two surveys indicated that 1.143 km3 of sediment were deposited in MDR during the 25 years of its operation. This implies that the reduction in its original storage capacity was 10.29% with an annual reduction rate of 0.441% which is less than the sedimentation rates in the worldwide and Middle East. Furthermore, the results showed that 0.563 km3 and 0.58 km3 of sediment were deposited in live storage and dead storage zones respectively. This indicates that the live and dead storage zones lost 6.9% and 19.66% of their storage capacity till 2011 respectively. According to these results, MDR’s useful life will be about 127 years or 121.5 years based on the depletion of its dead storage or 50% of its maximum storage capacity respectively. Likewise, the survey suggested new ASC curves for MDR. Comparison of the two TIN maps showed most of the sediment was deposited in the upper part of MDR, where the River Tigris enters MDR and it gradually reduced towards the dam site. There were erosion areas within the reservoir and mainly close to the dam body which might be due to dissolving the gypsum.In addition, fifty six sediment samples were collected from the bottom of its reservoir to study the nature of sediment deposited using the Van-Veen grab sampler. The samples were covering most of the reservoir area. The results revealed that the sediments were comprised of gravel, sand, silt and clay in the ratios 3.8%, 15%, 55.5% and 25.7% respectively. The distribution of these sediments indicates that the silt portion represents the highest or 77% of the bottom sediment of this reservoir followed by clay 13.5% and then sand with gravel 9.5%. However, sand percentages are the highest in the northern zone of the reservoir where the River Tigris enters the reservoir and decrease gradually towards the dam site. In the meantime, silt percentage decreases towards the dam site whilst the finer fraction (i.e. clay) increases. The sediment is poorly sorted, nearly symmetrical in skewness and leptokurtic, very leptokurtic, to mesocratic.Indirect approaches using several empirical and semi-empirical techniques to determine sedimentation characteristics in MDR were used. Three empirical approaches based on the particle grain size of the sediment deposited showed that MDR’s useful life ranged from 122.5 to 132 years. Six different empirical methods to determine the sediment trap efficiency (TE) of MDR were adopted. These methods were based on the residence time principle (water retention time). The methods were used to determine monthly TE and long-term TE for MDR for the period 1986 to 2011. The TE results with sediment entering MDR were used to calculate the amount of sediment deposited during its operational period. The comparison of the results with the bathymetric survey showed that all techniques gave good agreement, especially those depending on monthly TE, but the method that was proposed for large dams gave a more accurate result with 0.350% percentage error. To find out the sediment deposited depth at the Mosul dam site and to establish and predict changes in its ASC curves, four empirical and semi-empirical techniques were used for MDR. The results obtained were evaluated using the bathymetric survey data. The comparison of the results for establishing the ASC curves showed that one method agreed with bathymetric results whilst two methods gave good results for the sedimentation depth at the dam site. Furthermore, three of these methods were modified to predict the future changes in the ASC curves with sedimentation, based on the data from 11 reservoirs in the USA. The modified approaches were applied to MDR to predict the future ASC curves for 50, 75, 100 and 125 years. The curves predicted by these methods demonstrated compliance with the method adopted by the U.S. Bureau of Reclamation ‘area reduction method’. Finally, the indirect approaches can help decision makers, planners and designers, to monitor sedimentation characteristics and to implement prudent strategies for management of MDR in the future and to know the most suitable technique to adopt for MDR in the future.

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  • 25.
    Makusa, Gregory
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Stabilization-solidification of high water content dredged sediment: Strength, compressibility and durability evaluations2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dredging activities at ports and harbors are inevitable for safe navigation of ships and vessels. The outcomes of dredging are huge volumes of dredged materials, which can range from very fine and contaminated sediments to sands and gravels. The coarse sands and gravels can be directly used in civil engineering applications. The fine dredged sediments (DS) are usually associated with high water content, low shear strength, high compressibility and presence of contaminants. However, these unfavorable properties do not exclude the suitability of fined dredged sediments for use in geotechnical applications. Stabilization-solidification technology provides a comprehensive treatment method for improving strength, reducing the compressibility and mobilizing the contaminants to be less mobile.These properties make the stabilized fine dredged material (SDM) suitable for use in civil engineering applications (e.g. road embankment or structural backfill in land reclamation).However, stabilization-solidification is not a magic wand by which every geotechnical property is improved for better. In cold region climates, repetitive freeze–thaw cycles have detrimental effects to the strength and hydraulic properties of the SDM. Consequently, the applications and long term performance of the SDM under repetitive freeze-thaw cycles are still uncertain.Successful stabilization–solidification of the DS and the performance of the SDM depend on stabilization methods and materials. Process stabilization-solidification (PSS) is convenient technology for amending high water content DS with binders. The use of composite binders for stabilization–solidification of the DS is increasing due to increased artificial pozzolanas that can be used as supplementary cementitious materials (SCM). Primary binders such as cement can be supplemented with SCM (e.g. fly ash and ground granulated blast furnace slag). Cement hydration is a complex process with a complex series of unknown chemical reactions. The hydration of cement incorporating SCM is more complicated due to the co–existence of cement hydration and the pozzolanic reactions of the SCM. The fabric of dredged sediments formed under different physicochemical environments affects the reactivity of binders. The physic ochemical interactions between binders and the DS that influences the strength, compressibility and durability of high water content stabilized dredged sediment are examined and presented in this thesis. The findings of this study show that the use of fly ash (FA) and ground granulated blast furnace slag (GGBS) delays strength development of composite binder (CB)-treated DS. Irrespective of the amounts of CB, the improved strength depends on the amount of cement in the blend. The unconfined compressive strength increases with increasing the cement quantity Three phases of hydration mechanisms determine the compressibility behaviour of the SDM during curing. These are induction phase (IP), nucleation and crystallization phase (NCP), andhardening phase (HP). The IP occurs immediately after mixing. A protective layer is formed on the particle surface of binders, which prevent further penetration of water and then increases resistance to deformations. The evaluated tangent modulus increases to maximum value followed by abrupt drop to lower values at effective vertical stress, which is equals topreconsolidation stress. NCP follows when the protective layer changes to a more permeable membrane, which permits inward flow of water molecules, and outward migration of calcium ion and silicate ions. The tangent modulus of the SDM in NCP is small and increases linearly with effective vertical stress. The SDM in NCP is characterized by loss in apparent preconsolidation stress and tangent modulus. HP occurs as a result of increased thickness and stiffness of the protective layer. The compressibility of the SDM in HP is reduced significantly due to increased apparent preconsolidation pressure and tangent modulus. It is concluded that the maximum tangent modulus of untreated DS determines the maximum deformation of the SDM in all phases of hydration processes.Healing of the damaged SDM due to repetitive freeze-thaw action depend on the type of binder. The inclusion of SCM on one hand increases the healing of the SDM with reduced strength. This occurs during thaw consolidation. On the other hand, inclusion of SCM causes increased HC of the SDM. Considering healing potential on the damaged SDM with reduced strength, increased hydraulic conductivity causes increased rate of dissipation of excess pore pressure, reducedundrained conditions, and improved strength (enhanced outcome). In order to maintain its strength and hydraulic conductivity, the SDM requires protection from severe damage of repetitive freeze–thaw cycles. It can be beneficial to place the SDM below frost depth or use protective cover of geosythetic clay liners (GCL)

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  • 26.
    Al-Taie, Laith
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Performance of Clay Liners in Near-Surface Repositories in Desert Climate2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wars in Iraq (1991 and 2003) generated various types of hazardous waste (HW) in the form of soil contaminated by depleted uranium (DU). Other HW emanated from destroyed army vehicles and remnants of Iraqi nuclear facilities holding various types and amounts of chemical and radioactive material. The negative impact of the various wastes on the health conditions of the population was reported from different parts of Iraq, showing an enhanced frequency of cancer and abnormally born infants. For isolating the wastes, which represent low-level and short-lived intermediate level radioactive wastes, near-surface repositories (NSR) are proposed since they represent the least expensive way of solving future problems with sufficient safety. Internationally, the timeframe of the containment of such wastes is designated to be 300 years. Site selection affects and largely controls the selection of a suitable design the aim being to minimize or eliminate migration of hazardous elements from the waste to the environment. The formulation of siting criteria is the first vital step toward the resolution of the problem. Site selection criteria are proposed taking in account three major factors: environmental, geological and socio-economic factors. Accordingly, Iraqi deserts, which make up 60% of Iraq, represent the number one candidate for locating a safe disposal facility, primarily because of the low population, suitable topography, climatic conditions, seismic stability and availability of raw materials. Long-term performance of NSR is directly related to the function of top and bottom liner systems. They should be designed so that they are mutually compatible and combine to effectively isolate the waste. Liners are considered as the main elements of any disposal facility on the ground surface and a properly designed top liner system is of particular importance since it will minimize or eliminate water percolation into the waste body. Compacted clay liners (CCL) should preferably have with a low hydraulic conductivity, which is achievable by proper selection of raw materials, compaction density and construction methods. A further criterion is that they must not soften significantly by expansion on wetting, which puts a limit to the smectite content and density. The liners can consist of native material found near the landfill site, and be used after simple processing, primarily drying and crushing, or be mixed with fillers like silty sand. Since the hydraulic conductivity is the key property of a reliable CCL, relevant experimental determination of the hydraulic conductivity is vital. The common practice in geotechnical laboratories is to apply high hydraulic gradients for getting results quickly but this can lead to non-conservative, incorrect results. The present study involved determination of the hydraulic conductivity of a smectite-rich clay sampled at places within reasonable distance from potential NSR sites. Various hydraulic gradients were applied to samples compacted to several different densities, using two permeants and two filter types. It was concluded that the outflow filter can significantly affect the evaluated conductivity especially when applying high hydraulic gradients. This was partly explained by clogging of outflow filters of conventional fine-porous type by torn-off clay particles at such gradients. A major conclusion was that the gradient in laboratory testing should not exceed 100 m/m.In order to assess the suitability of available raw materials within the Iraqi Deserts, two smectitic soils termed as Green and Red clays were investigated for potential use in CCLs. Both clays are fairly rich in smectite, which calls for mixing them with properly graded silt/sand material from the desert for modifying the expandability. The shear strength, swelling pressure, hydraulic conductivity and creep properties were determined and used for defining criteria for selecting suitable clay-sand ratios. The results showed that 30-50% Green clay mixed with sand and 40-60% Red clay mixed with sand were suitable for constructing top liners with a hydraulic conductivity of 1×10-9 - 1×10-10 m/s. For bottom liners, 70% Green clay mixed with sand and 80% Red clay mixed with sand would be suitable; they were found to have a hydraulic conductivity of 1×10-11 m/s.The long-term performance of CCL is controlled by a number of processes like long periods of extreme dryness and short periods of very heavy rain. The percolation of water through the top liner system of a number of design alternatives were simulated using the code HELP 3.95D and subsequently by the FE program VADOSE/W. For the assumed NSR concept the slope stability of the top liner is essential and it was determined by using FE technique considering various slope angles. The engineering properties, primarily the hydraulic conductivity, swelling pressure and shear strength of 30-50% Green clay mixed with sand were introduced in the simulations. Two initial water contents of the compacted materials were considered representing 1) optimum water content (“wet case”), and 2) air‐dry conditions (“dry case”). Application of the HELP code decided the selection of suitable CCL having a thickness of 0.5 m and inclined by 5.7ᵒ. More detailed analyses with VADOSE/W showed that a mixture at the dry case would bring 0.5 mm (0.5 litre of leaking water per square meter) through CCL in an eight year simulation period. Long-term simulations (up to 300 years) showed that CCL would undergo continuous drying without reaching saturation even in the case of periods of very heavy rain (616 mm) for the wet and dry cases. The slope stability factor for the rather steep angle 30ᵒ was found to be 1.5 for the most critical case representing complete water saturation. In conclusion, the proposed materials and design features are believed to be suitable for practical application.

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  • 27.
    Zakaria, Saleh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rain Water Harvesting (RWH) North of Iraq2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Rainwater harvesting is one of the methods that can ensure availability of water for winter crop in Iraq. Using this technique the excess rainwater (runoff) is stored in reservoirs of dams of different sizes. The water from these reservoirs can be used later when required to satisfy the crops requirements. It is believed that rainwater harvesting will be one of the solutions to overcome water shortages problem in Iraq.This work includes four parts dealing with macro rainwater harvesting modeling. The study area includes selected sites at three Governorates located north of Iraq (Erbil, Sulaymaniyah, and Nineveh). In part one of the work, three selected sites at south, north and east of Sinjar district (Nineveh Governorate) were used. The slope of the study area at Sinjar district is less than 5%. The technique was first applied on southern Sinjar Mountain. Linear programming technique was adopted to optimize the irrigated area of barley crop for irrigation scenario of supplemental irrigation (SI) 100% of full irrigation requirements. Two scenarios of reservoir operation were considered for each main basin. In the first, each reservoir was operated as a separate unit while in the second all reservoirs in main basin were operated as one system. Both scenarios gave encouraging results. Scenario two however, was relatively better. The technique was applied again on the northern and eastern Sinjar Mountain area but with different catchments area and scenarios of irrigation (supplemental irrigation (SI) 100%, deficit irrigation (DI) 50%, and deficit irrigation (DI) 25% of full irrigation requirements). Wheat crop was considered as the main crop grown in the area. A linear programming technique was adopted to optimize the irrigated area for the above three scenarios of irrigation. The results of the three scenarios used indicated that, using deficit irrigation (DI) of 50% can be more beneficial than SI of 100% and DI of 25% of full irrigation requirements. Part two of the work includes application of Macro RWH technique at mountain areas in Northeastern part of Iraq. In these areas, all selected basins having slope more than 5 % and located at the rain-fed farms of Kurdistan region of Iraq, Erbil and Sulaymaniyah Governorates. The annual rainfall is greater than what was available at Nineveh Governorate. Part three of the work focused about the ability of Macro RWH technique to support wheat crop yield production in dry rain-fed farms at north Sinjar district, north west of Iraq, using wheat crop yield-water relationship that conducted by International Center for Agricultural Research in the Dry Areas (ICARDA). Three scenarios of supplemental irrigation (100%, 75% and 50%) of full irrigation. requirements with, various rainfall conditions were used, two types of wheat (bread and durum) were considered. Part four of the work focused on climatic change and future prospects for Macro RWH technique. Box-Jenkins methodology for time series analysis and forecasting (ARIMA model) was used to study future rainfall for 4 main rainfall stations surrounding Sinjar area in order to forecast expected rainfall for the period 2012-2016. Future rainfall depths were forecasted with adoption of a confidence level of 95%. The future rainfall was employed for RWH technique. This part also includes a review of the impact of climatic change on countries of the Middle East and North Africa (MENA region). The climatic model CGCM3.1 (T47) 2 was used to explain the changes in the average temperatures and rainfall on MENA region with special emphases on Iraq. Long term future seasonal rainfall during the period 2020-2099 at east Sinjar (Nineveh Governorate) showed a clear negative trend reflecting the reduction in total seasonal rainfall amount. For these future rainfall depths, the maximum, minimum and average harvested runoff volumes were estimated. The comparison of the runoff results between future and historical recorded rainfall for the same study area was carried out to show the future validity of rainwater harvesting. In order to estimate the amount of runoff that can be harvested from a given catchment area at eastern Sinjar, an attempt was made to provide set of charts that are easy to be used in order to estimate the equivalent harvested runoff depth (mm) for different selected rainfall depths under different hydraulic conditions for the catchment area. Macro rainwater harvesting (RWH) technique had been tested for future rainfall data that predicted by two emission scenarios of climatic change (A2 and B2) for the period 2020-2099 at Nineveh and Sulaymaniyah Governorates north of Iraq. The results of the four parts of the thesis reflect useful values for RWH and its influence to increase the irrigated area and then the crop yield in the studied region when combined with an effective system like supplemental irrigation. Rain-fed land in the studied areas requires effective technique in terms of saving significant runoff water for irrigation purposes and this might be achieved by rain-water harvesting (RWH) technique.

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  • 28.
    Zardari, Muhammad Auchar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical analyses of stability of a gradually raised tailings dam2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Numerical analyses are presented in this thesis to address potential stability problems that may occur during gradual raisings and under seismic loading conditions of Aitik tailings dam in northern Sweden. The dam is mainly raised using upstream construction method. It is planned to raise the dam gradually in several stages. Two dam parts were studied. The first dam part is a straight dam portion, and the second dam part is a corner. The main concerns associated with future raisings of the straight dam part were: (i) the stability of the dam could be affected by an increase in excess pore pressures during sequential raisings, (ii) how to gradually strengthen the dam by using rockfill berms as supports in such a way that required slope stability can be achieved with a minimum volume of rockfill berms, and (iii) if the dam is subjected to seismic loading, whether or not an increase in excess pore pressures could lead to extensive liquefaction which may cause a failure. The problems related to the dam corner were that tension zones and/or low compression zones could develop because of the horizontal pressure of the stored tailings on the inside of the curvature of the dam corner.Numerical analyses were conducted on both the dam parts using finite element method. Two dimensional (2D) plane strain finite element model was utilized to analyse the straight dam. The dam corner was analysed with both the three dimensional (3D) finite element model, and the 2D axisymmetric finite element model. Coupled deformation and consolidation analyses, and slope stability analyses were performed on both the dam parts to simulate gradual raisings, and to compute safety factors. In addition to this, dynamic analyses were carried out on the straight dam part to evaluate the potential for liquefaction, and seismic stability of the dam. The seismic behaviour of the dam was analysed for two cases: (i) a normal case (earthquake of 3.6 Swedish local magnitude), and (ii) an extreme case (earthquake of 5.8 moment magnitude).The results of the straight dam part, with only previously existing rockfill berms, indicate that stability of the dam was reduced due to an increase in excess pore pressures during raisings. Rockfill berms were utilized as supports to raise the dam with enough safety. An optimization technique was utilized to minimize the volume of rockfill berms. This technique could result in significant saving of cost of rockfill berms.The results of the dam corner show that tension zones and/or low compression zones were located on the surface of the dam corner, mainly above the phreatic level. It is interpreted that there is no risk of internal erosion through the embankments because no seepage path occurs above the phreatic level, and a filter zone exists along the slope of the dam. It is suggested to gradually strengthen the dam corner with rockfill berms. The results of the 2D axisymmetric analyses of the dam corner were in a fairly good agreement with those of the 3D analyses. This implies that the 2D axisymmetric analyses are valid for this dam corner. This is an important finding as 2D axisymmetric analyses require much less computational time compared to 3D analyses.The results of the dynamic analyses performed on the straight dam (including additional rockfill berms) suggest that, for the extreme case, liquefaction could occur in a limited zone that is located below the surface near the embankments. For both the normal and the extreme case, (i) seismically induced displacements seem to be tolerable, and (ii) the post seismic stability of the dam is considered to be sufficient.The findings of this study have been practically applied to the Aitik tailings dam. In general, the modelling procedure and the optimization technique to minimize volume of rockfill berms, presented in this study, could be applied to other tailings dams.

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  • 29.
    Zakrisson, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Numerical simulations of blast loaded steel plates for improved vehicle protection2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the past decade, there has been an increasing demand from governments for high level protections for military vehicles against explosives. However, the design and validation of protection is a time consuming and expensive process, where previous experience plays an important role. Development time and weight are the driving factors, where the weight influences vehicle performance. Numerical simulations are used as a tool in the design process, in order to reduce development time and successively improve the protection. The explosive load acting on a structure is sometimes described with analytical functions, with limitations to shape and type of the explosive, confinement conditions etc. An alternative way to describe the blast load is to use numerical simulations based on continuum mechanics. The blast load is determined by modelling the actual type and shape of the explosive in air or soil, where the explosive force transfers to the structure of interest. However, accuracy of the solution must be considered, where methods and models should be validated against experimental data. Within this work, tests with explosive placed in air, soil or a steel pot have been performed, where the blast load acts on steel target plates resulting in large deformations up to fracture. For the non-fractured target plates, the maximum dynamic and residual deformations of steel plates were measured, while the impulse transfer was measured in some tests. This thesis focuses on continuum based numerical simulations for describing the blast load, with validation against data from the experiments. The numerical and experimental results regarding structural deformation of blast loaded steel plates correlates relatively well against each other. Further, simulations regarding fracture of blast loaded steel plates show conservative results compared to experimental observations. However, more work needs to be undertaken regarding numerical methods to predict fracture on blast loaded structures. The main conclusion of this work is that numerical simulations of blast loading on steel plates, leading to large deformations up to fracture, can be described with sufficient accuracy for design purposes.

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  • 30.
    Bernander, Stig
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Progressive landslides in long natural slopes: Formation, potential extension and configuration of finished slides in strain-softening soils2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    After the large landslide in Tuve (Gothenburg, 1977), the author began developing a finite difference model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. In the model, the mean down-slope deformation in each element caused by normal forces is maintained compatible with the deformation generated by shear stresses. He developed software for the model and presented it at international soil mechanics conferences during the 1980-ies. In 2000 he summarized his findings in a Licentiate thesis. An easy-to-use spread-sheet has also been developed. In this thesis the author conveys his experiences of slide modeling focusing on the nature of triggering agents and the different phases that a slope may undergo before its stability becomes truly critical.

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  • 31.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Use of tyre shreds in civil engineering applications: technical and environmental properties2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    End-of-life tyres are a disposal problem regarding the large volumes produced every year. Tyre shreds are primarily produced to reduce the transportation volumes of end-of-life tyres after collection. Within the European Union, there is a ban for landfilling tyre material in order to reduce the total landfilling volumes and to encourage recycling measures. Until recently the main disposal option has been energy recovery in industrial processes. However, legislation acts has recently been taken in the European Union to encourage recycling and recovery of end-of-life-tyres and re-use of tyre materials in construction works is listed as one disposal option.Tyre shreds possess interesting technical properties that could be beneficially used in civil engineering applications. Some characteristic properties of tyre shred materials are the low density, high elasticity, low stiffness, high drainage capacity and high thermal insulation capacity. These properties open up possibilities for utilisation of the material in an innovative manner.The overall aim of this thesis work has been to describe and evaluate tyre shreds as a civil engineering construction material from environmental and technical point of view. The thesis work has included laboratory tests and full scale field tests to investigate technical and environmental properties of tyre shreds and to investigate the tyre shred material behaviour in a real road construction. Furthermore, the state-of-the-art knowledge in the area has also been analysed and presented.In the laboratory studies technical properties focused on compaction and compression behaviour of tyre shreds have been investigated. In a field study of a built road, tyre shreds has been tested and evaluated, during four years, as lightweight fill and frost insulation material. Environmental properties of tyre shreds, mainly leaching characteristics, have been studied in laboratory tests and monitored in two full scale field tests.Based on the results in the laboratory studies a model is proposed for evaluation of stressstrain properties and prediction of compression behaviour. Recommendations for construction works and pavement design are suggested based on the road construction field study results.Conclusions regarding the studied leaching properties of tyre shreds, based on the laboratory tests and the field monitoring, are that zinc and iron are the metals mainly released and that the release of the studied organic compounds, i.e. PAH and phenols, are low. From an environmental point-of-view focus should be moved from PAH-compounds towards other compounds that are more interesting from mobility perspective and lack of knowledge. It is concluded from this thesis work that PAH is not a pollution problem in the area of use of tyre material covered by this work.Applications where tyre shreds have been successfully utilised as construction material, are e.g. as draining layers in landfills and as material in trotting tracks and paddocks. The utilisation of the material in trotting tracks and paddocks is especially interesting since the unique elasticity of the material is utilised. The potential of utilising tyre shreds in civil engineering construction is big. Since the available amounts of material is limited there is a possibility to direct the use of tyre shreds to the most favourable applications of tyre shreds and still solve the disposal problem of end-of-life tyres.

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  • 32.
    Hermansson, Åke
    Luleå University of Technology.
    Modeling of frost heave and surface temperatures in roads2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Temperature and moisture are very essential parameters when describing the condition of a pavement. In most cases, a high moisture content involves a decreased bearing capacity and, consequently, a shorter durability of the pavement. A frozen pavement has a greater bearing capacity than the corresponding construction in spring or late autumn. However, the freezing itself also implies strains to the pavement, as it heaves to different extent and in different directions in connection with the frost heave. The properties of an asphalt concrete pavement vary dramatically according to temperature. Cold asphalt concrete is hard, stiff and brittle, and therefore, cracks easily occur, whereas its bearing capacity decreases at high temperatures as softening progresses. Emphasizing the asphalt concrete, a numerical model has been developed for calculation of temperatures for summer condition, by means of recorded values for solar radiation, air temperature and wind velocity. Further, in order to also model temperatures and other conditions, occurring in the pavement during winter, a frost heave module has been developed and included in the model. The aim of this is to gain a better insight into the freezing process of a road structure. The model also provides an efficient tool for a better understanding of important factors related to frost depth and frost heave. A modified version of the model, is tested for falling weight deflectometer analysis. Input here, is a series of measured pavement surface temperatures and the output is calculated temperature distributions for the asphalt layer. Measuring equipment, developed at VTI, has been used to, in the field, automatically record frost heave and pavement temperature distribution. Furthermore, equipment for freezing tests in laboratory has also been developed. Experiences from such tests and field measurements have been used when developing the numerical model for freezing of pavements. At the laboratory freezing tests, a special interest has been devoted to water intake rate and heave rate related to cooling rate. The experiences, obtained from both the laboratory tests, as well as the field observations, have been compared to what has been reported in literature. Temperatures obtained from the numerical model for summer and winter temperatures have turned out to correspond well to measurements of pavement temperatures at all test sections studied, 12 in US and 3 in Sweden. The freezing tests in laboratory have shown, that a strong frost heave can exist without addition of external water to the samples. The natural water content is, consequently, sufficient to provide enough water for the heave. This "in-situ" water can be redistributed in the structure, thus providing water to the frozen portion of the profile to cause significant frost heave. Frost heave caused by a process like this, is not bound to uptake of external water, which normally is assumed in the relevant literature. Frost heave in freezing tests is often explained by 10 % volume expansion of the freezing water, which is sucked up by samples during the test. The freezing tests in laboratory have also shown, that the ratio (heave/water uptake) increases with frost susceptibility, i.e. the most frost susceptible soils require comparatively less added water for the heaving. The freezing tests in laboratory and field tests, have also shown that the relation between heave rate and heat extraction rate at the frost front, is weak. This is also in contradiction to what normally is stated in literature. The weak relation is found during longer periods of continous frost penetration. However, when heat extraction rate is varied at short time intervals, a strong dependency between heave rate and heat extraction rate is found.

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  • 33.
    Westerberg, Bo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Behaviour and modelling of a natural soft clay: triaxial testing, constitutive relations and finite element modelling1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objectives if the research project have been to create an experimental basis for a more general theoretical modelling of Swedish clays and to improve the knowledge of the mechanical behaviour of natural soft clays. Another objective has been to investigate the effects of end restraint on the mechanical behaviour obtained in triaxial tests, by means of numerical simulations. Extensive experimental studies were performed by triaxial tests on a natural soft clay from the city of Norrköping. The results are discussed in detail from a quantitative and qualitative point of view and the effects of the in situ structure of the clay on the mechanical behaviour focused. Undrained and drained shear conditions are investigated. Obtained deformation modes in triaxial tests ar classified and analysed. Soil parameters for constitutive models are evaluated and discussed and requirements formulated for a constitutive model supposed to describe the behaviour of the clay.

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  • 34.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    On a mathematical basis for constitutive drivers in soil plasticity1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Huvudsyftet med denna avhandling har varit att vidareutveckla en matematisk grund för konstitutiva drivenheter inom området plasticitetsteori för jord. Med en konstitutiv drivenhet avses här en datorrutin som innehåller ett antal utvalda konstitutiva modeller jämte integrationsmetoder och med vilken olika laboratorieförsök och fältförsök kan simuleras numeriskt och modellparametrar bestämmas genom optimering. De konstitutiva ekvationer som utgör den matematiska basen i drivenheten, och i vilka materiamodellema implementeras, har formulerats som inkrementella tangentsamband under blandad styrning för simulering av jords såväl dränerade som odränerade beteende. Blandad styrning innebär att kontrollvariablerna kan väljas som en blandning av spännings- och töjningskomponenter. De mot kontrollvariablerna associerade spänningarna/töjningarna blir då simuleringens responsvariabler. Inom forskningsprojektet har en metod för korrigering av spänningspunktens avdrift från flytytan vid explicit integrering och blandad styrning utvecklats för såväl dränerat som odränerat tillstånd. Vidare har en optimeringsrutin för identifiering av modellparametrar utgående från resultat från olika experimentella försök utarbetats. För kontroll av det matematiska konceptet har en generell och användarvänlig konstitutiv drivenhet utvecklats, i form av ett PC-program. Slutligen har effekterna av ändytefriktion och axiell töjningshastighet vid konventionella triaxialförsök analyserats genom numerisk simulering av försöksförfarandet med finita elementmetoden. Studien visar på att randeffekter bör beaktas vid utvärdering av triaxialförsök, t ex genom att utnyttja optimering också på nivån för randvärdesproblemet. Av den vid tillämpningen av den konstitutiva drivenheten vunna erfarenheten kan man dra slutsatsen att den matematiska basen, dvs det blandade tangentsambandet, korrektionsmetoden för avdrift och optimeringsrutinen, fungerar som avsett samt att programmet har en bra struktur. En konstitutiv drivenhet kan utnyttjas i forskning och undervisning men har också praktisk tillämpning. Inom forskningen existerar ett flertal olika tillämpningar såsom utvärdering och jämförelse av uppförandet hos etablerade liksom nyutvecklade konstitutiva modeller samt känslighetsanalys av modellparametrar, antal integrationssteg etc. Den konstitutiva drivenheten har även visat sig vara ett användbart pedagogiskt verktyg för att lättare kunna förstå olika jordmodellers beteende. Ett viktigt exempel på praktisk tillämpning, i samband med användning av finita elementmetoden för lösning av ett geotekniskt problem, är som hjälpmedel för valet av lämplig konstitutiv modell för ifrågavarande jordmaterial och problem liksom för bestämningen av rimliga värden på de i materialmodellen ingående parametrarna. Eftersom så många viktiga tillämpningar existerar för konstitutiva drivenheter vore det fördelaktigt om sådana program också vore lättåtkomliga i form av komplementprogram till kommersiell programvara.

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  • 35.
    Mácsik, Josef
    Luleå University of Technology.
    Soil improvement based on environmental geotechnics: environmental and geotechnical aspects of drainage of redox-sensitive soils and stabilisation of soils with by-products1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [sv]

    I avhandlingen behandlas Miljögeotekniska problem som "dränering av redox-sensitiva jordar", "blockstabilisering av sulfidjord och torvjord" och " undersökning av nya vägmaterial". - Miljöproblem, kopplat till dränering och/eller urgrävning av redox-sensitiva jordar, som järnhaltiga moräner och sulfidjordar, behandlas i denna avhandling. Dräneringsproblem, orsakat av igensättning och korrosion, kan förutses genom att bedöma jord- och grundvattenkemin hos jord- respektive grundvattenprover. -Blockstabilisering är en grundläggningsmetod som används i organiska jordar, där dränering och urgrävning bör undvikas. I denna avhandling behandlas stabilisering av sulfidjord och torvjord med Portlandcement, Portlandcement/ Hyttsten och Portlandcement/LD-slagg. För kontroll av homogenitet hos stabiliserade fältprover från sulfidjord och torvjord har metoder, för respektive jord, tagits fram och föreslagits. Resultaten visar att stabilisering med Portland-cement och Hyttstenbaserade tillsatsmedel fungerar tillfredsställande, utan att de stabiliserade materialens halter av reglerade element/föreningar överskrider svenska riktvärden för känslig markanvändning. Portlandcement/LD-slagg ger bra stabiliseringsresultat men LD-slagg innehåller höga halter av lakbart Vanadin. - Geotekniska egenskaper hos ett jord- eller vägmaterial kan förbättras genom tillsättning av restprodukter som tillsatsmedel. Miljögeoteknisk undersökning bör därför utföras.

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  • 36. Ask, Maria
    In-situ and laboratory stress investigations using borehole data from the North Atlantic Ocean1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis presents results from investigations ofin-situ and laboratory stress from borehole logging andlaboratory deformation experiments on drill-cores. The datacome from hydrocarbon exploration and production wells in theDanish Sector of the North Sea, and from boreholes drilled bythe Ocean Drilling Program (ODP). The drill-core samples werecollected from two ODP boreholes in the equatorial and easternAtlantic Ocean. The objectives for this project are: (1) to collect datafrom the North Atlantic Ocean where few or no stressmeasurements exist, and to incorporate the data into the WorldStress Map (WSM); (2) to determine the source of stress thatgenerates the mean orientation of the maximum horizontal stressin individual boreholes in ocean areas; and (3) to study themechanical responses of sediments and rocks in order tounderstand the nature of stress and stress paths that producedeformation of the ocean floor. The orientations of in-situ horizontal stresses weredetermined from analyses of borehole breakouts anddrilling-induced fractures (DIFs) as determined from four-armcaliper and Formation MicroScanner (FMS) data. Logging datawere analyzed using graphical and automated programs, usingbreakout and DIF criteria, directional statistics, and theborehole data were ranked according the WSM ranking system. Stress data from 44 oil wells and ODP boreholes in the NorthAtlantic Ocean represent important additions to the WSM fromareas where few stress data were available. Despite of theirrelatively shallow total depths, it is suggested that thestress orientation in many of the ODP boreholes are influencedby plate boundary forces. The observed variation in downholedistribution of breakouts in the oil wells and the lack ofregional trends indicate that local and regional stress sourcescontrol the stress field in these wells. Detailed laboratory stress measurements were conducted in atriaxial cell mounted in a servo-hydraulic load frame, usingreconsolidation and triaxial tests on small sub-samples fromtwo drill-core samples of different lithologies. Results from tests on a claystone from the basal section ofthe ocean-continent transition in West Iberia margin suggestthat the in-situ effective stresses are low because of the highpore pressure. The fractured nature of the underlying basementand breccia suggest that the pore fluids originate from deepersections. Results from tests on a calcarenite from about 1 kmdepth show that the elastic versus elastic-plastic behaviordiffers significantly, but that the rock behavior can bedescribed by critical state soil mechanics.

  • 37.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Soil behavior at freezing and thawing1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Avhandlingens första del behandlar en teoretisk beräkningsmodell för tjällyftning samt studier av dess noggranhet i olika situationer. Tjällossningsförloppet analyseras och studeras genom noggranna mätningar av porvattentryckens fördelning i tid och rum. Porvattentrycksutvecklingen kopplas till läget av islinserna i jorden, som detekteras med hjälp av röntgenteknik. Avhandlingens andra del belyser hur frusen jord kan packas och vad deformationerna i sådan jord blir då den tinar. Beräkningar av kompressionen i samband med upptining jämförs med resultat från såväl laboratorieförsök som uppföljningar i fält. Strukturella förändringar i jorden till följd av frysning och tining belyses också.

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  • 38.
    Viklander, Peter
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Compaction and thaw deformation of frozen soil: permeability and structural effects due to freezing and thawing.1997Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is the result of the two projects:"Deformations in winter compacted soils" and "Permeability changes in a fine-grained till due to freeze/thaw". The aim of the first project was to study whether it is possible to compact frozen soils, in road embankments etc., to a satisfying result as well as to identify the most important factors influencing the compaction result. Different types of soil (fine-grained till and sand) were compacted in the laboratory at the temperatures +20, -2 and -10°C using compaction cylinders of two different sizes (1 dm³). Frozen soil cubes, having a side-length of 5 to 100 mm, were manufactured at different water contents and compacted in frozen state. The tests show that the compaction result decreases with decreasing temperature and increasing water content. However, the influence of the size of the soil cubes was of minor importance and the influence of the testing temperature was significantly smaller than what has been reported in the literature. In addition, compression tests on frozen, compacted soil samples were carried out to measure the thaw settlement. A relation ( a-value), based on the dry density of the frozen and unfrozen soil, was established from which it is possible to estimate the maximum compression taking place when the frozen soil thaws and is loaded. The aim of the second project was to investigate whether structural changes take place in a fine-grained till exposed to cyclic freezing and thawing. It was believed that freeze/thaw cycles could have a negative impact on fine-grained till, e.g. on its function as a hydraulic barrier. The permeability was chosen to be the key parameter to study whether the structure was affected of freezing and thawing or not. In addition, tests were directed to measure possible movements of small particles and stones due to freezing and thawing. In the laboratory, unfrozen soil was compacted to different void ratios into a rigid wall opermeameter and the permeability was measured. Thereafter, the sample was frozen and thawed a number of cycles. The samples were frozen one dimensionally in a closed pore water system and the permeability was measured in the thawed soil after a certain number of cycles. In addition, the particle movements were measured by granulometric tests and the stone movements by a specially developed X-ray technique. The investigations showed that the permeability in a fine-grained till is influenced by the freeze/thaw cycles. Typically, the permeability increased by 1 to 10 times in an initially dense till and decreased between 1 to 50 times in an initially loose till. The soil exhibited volume changes due to the freeze/thaw cycles and the volume typically decreased for an initially loose soil and increased for a dense soil. A residual void ratio was reached after 1-3 freeze/thaw cycles, independent of the state of the soil structure prior to freezing. The residual void ratio ranged from 0.31 to 0.40 in the studied material. Finally, no particle movements were detected, but significant stone movements in vertical as well horizontal direction were identified.

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  • 39.
    Sheng, Daichao
    Luleå University of Technology.
    Thermodynamics of freezing soils: theory and application1994Doctoral thesis, comprehensive summary (Other academic)
  • 40.
    Yu, Yao
    Luleå University of Technology.
    Testing and modelling of silty and sulphide-rich soils1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silt and sulphide soil are two types of soil which are dominating in northern Sweden, especially in the coast area of the Baltic sea. The stress-strain and strength characteristics of these two soils have so far not been as much explored as those for e.g. Scandinavian clays. With increasing use of numerical methods in geotechnical engineering, better knowledge of the constitutive behaviour of soils is needed as well as more accurate models. The work reported in this thesis is an attempt to achieve such a knowledge for silt and sulphide soil. The drained and undrained stress-strain characteristics of silt have been investigated by means of triaxial compression and extension tests. The compressibility, the dual characteristic of contractancy and dilatancy during shearing, the effect of the clay content and the dependence of the failure surface on the Lode angle have been specially discussed. The drained and undrained stress-strain characteristics of sulphide soil were investigated by means of triaxial and CRS oedometer tests. The compressibility, the effect of the excess pore pressure and the anisotropy have been specially discussed. A plasticity model was proposed for modelling the constitutive behaviour of silt. Among others, the model takes into account the dual characteristic and the dependence of the yield criterion on the Lode angle. An analytical solution was carried out for the undrained triaxial state which links the dilatancy parameter to other parameters. Conditions of material stability were also derived for the triaxial stress state. A plasticity model was proposed for modelling the constitutive behaviour of sulphide soil. Among others, the model takes into account the cohesion and the initial and stress-induced anisotropy. An explicit relation was derived to relate failure or critical state parameters in the isotropic case to those in the anisotropic (K0) case. A calibration method based on optimization was designed to improve the overall quality of model parameters. By using this method, the two proposed models were then calibrated to experimental data from several sets of tests on silt and sulphide soil. Two boundary-value problems, with available data from field tests, were analyzed using a finite element code with the proposed models implemented to demonstrate the capability of the proposed models and of the numerical method.

  • 41.
    Carlsson, Torbjörn
    Luleå University of Technology.
    Interactions in MX-80 bentonite/water/electrolyte systems1986Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main objective of this work was to study the influence of temperature, water ratio and electrolyte content on the molecular water mobility in water saturated MX-80 bentonite. T a minor extent the influence of pressure, time, and specific surface area on the molecular water mobility was studied. The investigation was carried out by pulsed nuclear magnetic resonance technique, NMR. The proton T2 relaxation time was chosen as a measure of the molecular water mobility. The investigated samples consisted of MX-80 bentonite to which water solutions of either NaCl, KCl, CaCl2, or SrCl2 were added. The electrolyte concentration varied between 0 and 0.35 mol.dm-3. The water ratio varied between 23 and 2000 per cent. The electrolyte content and water ratio were kept within limits corresponding to non-flocculated MX-80 bentonite. The sample temperature varied between +15 and +80°C. The structure of montmorillonite, the main component in MX-80 bentonite, and the structure of liquid water as well as the main physico-chemical interactions taking place in the investigated MX-80 bentonite samples are discussed.

  • 42.
    Börgesson, Lennart
    Luleå University of Technology.
    Mechanical properties of inorganic silt1981Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The need for increased knowledge of the properties and behaviour of silty soils has been urgent for many years. This report is an attempt to fulfil this need to same degree. The properties of inorganic silt have been investigated by means of laboratory tests, field tests and load tests. The investigations have primarily concerned drained and undrained shear strength parameters and their use for real cases of load. The mechanisms of failure and the components of friction and shear strength are discussed. The influence of failure criteria, testing method, and rate of shear on the shear strength parameters have been studied as well as the influence of clay content, plasticity index, deformation to failure, and stress history. The testing methods and parameters have been checked with some load tests in the field and in the loading basin.

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