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  • 1.
    Toromanovic, Jasmina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Utvärdering av dammars tillstånd2018In: SwedCOLD Nyhetsbrev, no 2, p. 14-15Article in journal (Other (popular science, discussion, etc.))
  • 2.
    Zardari, Muhammad Auchar
    et al.
    Quaid-e-AwamUniversity of Engineering, Science and Technology, Nawabshah.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ormann, Linda
    Fortum, Power Division, Renewable Energy, Våxnäsgatan 10, Box 2087, SE-65002 Karlstad, 8 Sweden.
    Comparison of three-dimensional and two-dimensional axisymmetric finite element analyses of a corner section of a tailings dam2017In: Scientia Iranica. International Journal of Science and Technology, ISSN 1026-3098, E-ISSN 2345-3605, Vol. 24, no 5, p. 2320-2331, article id 9Article in journal (Refereed)
    Abstract [en]

    This paper presents three dimensional (3D) and two dimensional (2D) axisymmetric finite element analyses of a corner of a tailings dam. The analyses were performed to: (i) locate tension and/or low compression zones and to evaluate slope stability during sequential raising of the dam corner, and (ii) find whether the results of 2D axisymmetric analyses can be reliable for the dam corner. The corner is a potentially weak section of the dam where tension and/or low compression zones may develop. Development of such zones inside the dam corner can lead to cracks and initiation of internal erosion. The results of both the 3D and 2D axisymmetric analyses indicated that (i) tension and/or low compression zones were located in vicinity of surface of the dam corner mainly above the phreatic level, and (ii) the dam corner is stable up to the planned height if it is gradually strengthened with rockfill berms on the downstream side. The results of 2D axisymmetric analyses showed a fairly good agreement with those of 3D analyses. It is concluded that 2D axisymmetric analyses are appropriate for this dam corner. This implies that significant computational time can be saved by utilizing 2D analyses instead of 3D analyses.

  • 3.
    Toromanovic, Jasmina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of Measurement Error on the Genetic Algorithm in Soil Parameter Identification for an Earth- and Rockfill Dam2017In: ICSMGE 2017: 19th International Conference on Soil Mechanics and Geotechnical Engineering, 19th ICSMGE Secretariat , 2017, p. 2443-2446Conference paper (Refereed)
    Abstract [en]

    It is usually difficult to determine values for soil parameter values in earth- A nd rockfill dams by traditional methods. Field sampling is not easily performed, especially in the impervious parts, since the performance and safety of the dam structure may be affected in an unfavourable way. Therefore other methods, preferably non-destructive, are needed to investigate the mechanical behaviour. Inverse analysis has been utilised to identify soil parameter values for an earth- A nd rockfill dam. An error function and a genetic search algorithm were combined with a finite element software to perform the analysis. The model parameters in the chosen constitutive model were calibrated until the horizontal deformations corresponded to the horizontal inclinometer deformations. Errors or irregularities in field measurements can occur, for instance based on the accuracy of the equipment. In this study, the performance of the genetic algorithm was investigated, when applied to identify soil parameters for a dam. Added perturbations to simulated inclinometer data are randomly generated within a chosen interval of error. The results showed that the genetic algorithm found a minimum for the error function even though the field data was substantially perturbed. Errors up to 10% were shown to have minor impact

  • 4.
    Toromanovic, Jasmina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of random measurement error on the genetic algorithm in soil parameter identification for an earth- and rockfill dam2017Conference paper (Other academic)
  • 5.
    Gunnvard, Per
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Evaluation of triangular pile arrangement through a numerical study of the light embankment piling method2017Conference paper (Refereed)
    Abstract [en]

    Embankment piling is a widely used foundation method in geotechnical engineering and the design is mostly based on empirical studies found on experimental or field evidents. Several studies have been conducted to capture the behaviour of embankment piles by means of numerical models. One of the issues is to simulate the arching effect between the piles. This has raised the question of the optimum pile arrangement. Along the northern coast of Sweden, where soft soil types and dense woodlands are common, timber piles have often been used in piled road and railway embankments. The pile group is designed as a semi-floating deep foundation in soft soil, where the piles are resting on top of the locally common firm glacial till bottom layer, naming the method light embankment piling. The Swedish design guidelines recently changed from a square to a triangular pile arrangement. However, the motivation of the changed lacked research which raised the question of optimal pile arrangement and centre-to-centre pile distance. This project aims to optimise the light embankment piling method through numerical analysis, verified by field and laboratory experiments. The optimisation will mainly focus on pile arrangement and centre-to-centre pile distance.

  • 6.
    Auchar Zardari, Muhammad
    et al.
    Quaid-e-Awam University of Engineering Science and Technology: Nawabshah, Pakistan.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Khalid, Muhammad S.
    Department of Urban Management, Kyoto University, Kyoto, Japan.
    Ask, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lund, Björn
    Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Numerical Analyses of Earthquake Induced Liquefaction and Deformation Behaviour of an Upstream Tailings Dam2017In: Advances in Materials Science and Engineering, ISSN 1687-8434, E-ISSN 1687-8442, Vol. 2017, article id 5389308Article in journal (Refereed)
    Abstract [en]

    Much of the seismic activity of northern Sweden consists of micro-earthquakes occurring near postglacial faults. However, larger magnitude earthquakes do occur in Sweden, and earthquake statistics indicate that a magnitude 5 event is likely to occur once every century. This paper presents dynamic analyses of the effects of larger earthquakes on an upstream tailings dam at the Aitik copper mine in northern Sweden. The analyses were performed to evaluate the potential for liquefaction and to assess stability of the dam under two specific earthquakes: a commonly occurring magnitude 3.6 event and a more extreme earthquake of magnitude 5.8. The dynamic analyses were carried out with the finite element program PLAXIS using a recently implemented constitutive model called UBCSAND. The results indicate that the magnitude 5.8 earthquake would likely induce liquefaction in a limited zone located below the ground surface near the embankment dikes. It is interpreted that stability of the dam may not be affected due to the limited extent of the liquefied zone. Both types of earthquakes are predicted to induce tolerable magnitudes of displacements. The results of the postseismic slope stability analysis, performed for a state after a seismic event, suggest that the dam is stable during both the earthquakes

  • 7.
    Gunnvard, Per
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical Analysis of the Mechanical Behaviour of Light Embankment Piling2017In: ICSMGE 2017: 19th International Conference on Soil Mechanics and Geotechnical Engineering / [ed] Woojin Lee, Jong-Sub Lee, Hyun-Ki Kim, Dong-Soo Kim, 19th ICSMGE Secretariat , 2017, p. 749-752Conference paper (Refereed)
    Abstract [en]

    2D and 3D finite element simulations were performed to investigate the mechanical behaviour of the light embankmentpiling method as a pre-study to further develop a new Swedish design guideline. The light embankment piling method is used forsulphide soils and utilises timber piles as its key feature. The Swedish Transport Administration (Trafikverket) recently changed thenational standard of the light embankment piling method from the use of a square to a triangular pile arrangement, based on a theory thata triangular arrangement creates more stable arches in between the piles. The objective with the present study is to evaluate the currentstandard by modelling setups with square and triangular pile arrangements with varying centre-to-centre distance. Both, completelyfloating and semi-floating pile groups were modelled here. The evaluation mainly focused on comparing embankment settlements as wellas axial forces in the piles. No evident difference in the mechanical behaviour between the triangular and the square piling pattern wasfound. The maximum allowed centre-to-centre distance can potentially be increased from 1.2 to 1.5m; resulting in approximately 30% fewer piles used.

  • 8.
    Toromanovic, Jasmina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Laue, Jan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Use of parameters identified by inverse analysis in an earth- and rockfill dam application2017In: 85th Annual Meeting  of International Commission on Large Dams, 2017Conference paper (Refereed)
  • 9.
    Toromanovic, Jasmina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Sipola, Johanna
    ÅF Hydropower Industry.
    Effects on an earth and rockfill dam undergoing dam safety measures2016Conference paper (Refereed)
    Abstract [en]

    Over the lifetime of a dam several measures are usually taken in order to assure the stability and the performance of the dam. In this case a hydropower dam in Northern Sweden is in need of dam safety measures. The question arose, what consequences there might be when such measures are performed. In order to estimate these effects, simulations have been carried out in the finite element programme PLAXIS 2D. Thereby, the deformations and the stability of the dam for the planned work can be evaluated. The performed simulations are based upon previously conducted research at Luleå University of Technology, where soil parameters in the investigated dam were identified by a method of inverse analysis.Three sections have been analysed: A, B and C. In section A increasing pore water pressure has been observed at the downstream side of the dam. Thereby it has been concluded that a new drainage system is needed; new trenches of large size are to be excavated. In section B new toe berms are planned, due to the requirement that the dam should be able to divert leakage without erosion occurring at the dam toe. This contains soil material that might degrade when stresses are increased, with intensified deformations as a consequence. In section C a new berm is to be constructed, before this can be conducted an excavation is performed at the toe of the dam.The results have shown deformations of an acceptable magnitude and factors of safety that indicate conditions for the planned dam safety measures. Numerical values of deformations and factors of safety can be utilised as an attempt to establish alarm values for the stability of the dam. The finite element method is a useful tool for this kind of evaluation.

  • 10.
    Axelsson, Kennet
    et al.
    Professor emeritus i byggnadskonstruktion vid Uppsala universitet.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Geoteknik2016Book (Refereed)
    Abstract [sv]

    Geoteknik behandlar jordmaterials mekaniska och tekniska egenskaper, kunskaper som är av betydelse för utförandet av en säker och stabil grundläggning av byggnader och anläggningar. Ämnet stödjer sig på kvartärgeologin, d.v.s. de lösa jordarternas geologi, samt på mekaniken och främst då deformerbara fasta kroppars mekanik. Geoteknik är ett semiempiriskt ämne, d.v.s. provning och erfarenhet ligger också till grund för de metoder som tillämpas.Boken är uppdelad i fyra huvuddelar. I del A ges en introduktion till ämnet samt en återblick på byggnadsgeologin (kvartärgeologin). I del B behandlas jordmaterialläran, d.v.s. jords kemiska och fysikaliska egenskaper vad gäller beståndsdelar, klassificering och strukturell uppbyggnad. Del C behandlar jordmekaniken, d.v.s. mekaniska och hållfasthetstekniska egenskaper hos jord. I del D tillämpas de inhämtade kunskaperna på viktiga geotekniska problemområden såsom bestämning av spännings­tillstånd i jordprofiler, beräkning av byggnaders och anläggningars sättning och geotekniska bärförmåga samt bestämning av jordtryck mot stödkonstruktioner och av jordslänters stabilitet.Geoteknik vänder sig i första hand till studenter på de tekniska hög­s­kolornas program för väg- och vattenbyggnad och samhällsbyggnad samt på högskolornas byggingenjörsprogram.

  • 11.
    Hassellund, Lovisa
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical analysis of an upstream tailings dam2016In: Proceedings of Nordic Conference on Soil Mechanics and Geotechnical NGM: Reykjavik, Iceland 25th – 28th of May 2016, 2016, p. 727-736Conference paper (Refereed)
    Abstract [en]

    This paper presents a case study of how the finite element methodcan be utilized to analyze stability of upstream tailings dams. Upstream tailings dams are usually raised gradually and the increased load normallyinfluencesthe stability in an unfavorableway;the load generatesexcess pore water pressures and reduced stability. In this study, an upstream tailings dam in Northern Sweden wasnumericallysimulated with the finite element software PLAXIS 2D in order to assess the stability of the dam. Upstream tailings dams are sensitive to high raising rates since initiated excess pore water pressures might not have time to dissipate. Stability analysis of a tailings damis an application that is very suitable to carry out using finite element software; once a finite element model of thecomplex geometry of adam has been established, it is easy to stepwiseadd new soil volumes, associated with each new raising, to the model.In this case study, it was found that strengthening actions were needed in order to maintain a stable structure. Rockfill berms weregradually added onthe downstream slope of the model to obtaina factor of safety above a recommended value. The volumes of rockfill needed for the berms wereminimized by numerical optimization to reduce costs. The stability betweenthe years2024 and2034 was analyzed; with an annual deposition cycle. The performednumerical studyresulted in a future plan for placement of rockfill berms to establishsufficient stability ofthe tailings dam. It was found that the volume of rockfill in the berms needed, varied during the years studied. Numerical modeling, as presented in this paper, is a useful tool for the dam owner to plan and design for future raisings of a tailings dam

  • 12.
    Hassellund, Lovisa
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical Simulations of Stability of a Gradually Raised Upstream Tailings Dam in Northern Sweden2016In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 21, no 13, p. 4699-4720Article in journal (Refereed)
    Abstract [en]

    This paper presents a case study where numerical modeling, with the finite element method, has been utilized to assess future stability of a tailings dam in Northern Sweden. The finite element software PLAXIS was utilized to simulate future dike raisings for the years 2024 to 2034. The simulations were conducted by computing each dike raising, the subsequent consolidation of the soil and the stability of the dam during the process. The factors of safety directly after each dike raising resulted in values continuously below a recommended value of 1.5. To increase the dam stability, rockfill berms were stepwise added on the downstream slope of the dam. An optimization technique was applied to place as small volumes of rockfill as possible in the berms at the most suitable locations on the downstream slope. By adding various volumes of rockfill in the berms each year, sufficient stability of the dam was obtained in the simulations. The excess pore water pressures increased annually in the simulations. It was shown that the excess pore water pressures did not totally dissipate before the following dike was constructed. The highest excess pore water pressures were located deep in the impoundment and did not have large effects on the dam stability.

  • 13.
    Elhami, Ehsan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ask, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Physical- and geomechanical properties of a drill core sample from 1.6 km depth at the Heletz site in Israel: Some implications for reservoir rock and CO2 storage2016In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 48, no 1, p. 84-93Article in journal (Refereed)
    Abstract [en]

    We have measured physical- and geomechanical properties of a core sample that was collected from 1.6 km depth at the Heletz site in Israel, within reservoir rock, layer A. The core sample is composed of poorly consolidated sandstone, with several layers of coarser grain sizes. Average bulk density and porosity are 1.93 ± 0.11 g/cm3 and 36 ± 5%, respectively.Both nondestructive and destructive tests have been made on the core sample and its subsamples, including CT-scanning, oedometer tests, drained direct shear tests, as well as measurements of index properties, X-ray fluorescence and X-ray diffraction. These tests provide an initial evaluation of the properties of the reservoir rock, but are far from capturing epistemic variability of the reservoir rock. The results support the macroscopic observation, that the sample is poorly consolidated compared to its depth of deposition. The effective pre-consolidation pressure is less than 0.2 MPa and the maximum peak shear strength obtained is less than 1 MPa (normal stress = 1 MPa). In comparison, effective vertical stress from weight of the overlying rocks is estimated to 14 MPa using the average bulk density of the core. All measurements suggest that our reservoir rock sample is extremely weak with respect to its depth of deposition.

  • 14.
    Elhami, Ehsan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ask, Maria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Erlström, Mikael
    Geological Survey of Sweden.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Physical Properties of Core Samples from the Swedish Part of the Southern Baltic Sea: Implications for CO2 Storage2016In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 97, p. 356-363Article in journal (Refereed)
    Abstract [en]

    This paper presents the results from a series of physical measurements conducted on core samples from the Swedish part of the southern Baltic Sea. The samples consist of 16 Cambrian sandstone samples (potential reservoir rock) and 9 Ordovician limestone samples (potential caprock). The two rock types reveal contrasting properties; axial P-wave velocity and density for the sandstone samples are 3.14±0.95km/s and 2.26±0.12 gr/cm3, respectively while for the limestone samples they are 6.09±0.22km/s and 2.58±0.08 gr/cm3, respectively. The scatter of the evaluated properties indicates aleatory variability and epistemic uncertainty in the properties which can be better addressed by further tests on more samples.

  • 15.
    Kahlström, Mats
    et al.
    Subsea 7.
    Frossard, Remi
    Subsea 7.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Predicted and observed settlements of a subsea rock installation: comparison between field measurements and FE simulations of soft North Sea clay2015In: Frontiers in offshore geotechnics III: proceedings of the Third International Symposium on Frontiers in Offshore Geotechnics (ISFOG 2015), Oslo, Norway, 10-12 June 2015 Volume 1 [...] / [ed] Vaughan Meyer, Boca Raton: CRC Press/Balkema , 2015, p. 393-398Conference paper (Refereed)
    Abstract [en]

    In this paper, a study is presented on the possibility to numerically simulate observed settlements of an offshore subsea rock foundation installed on normally consolidated clay. Settlements were monitored at 31 days and 200 days after installation and compared against predictions computed by means of finite element analysis. The results highlight that computations with a material model incorporating a logarithmic stress-strain relationship can accurately predict the consolidation settlements of normally consolidated clay. For long-term settlements, a material model that includes a creep factor is likely to increase the prediction accuracy of the total settlements. This study was performed in order to improve the prediction of soft clay settlements, as this phenomenon may have a large impact on design for sensitive subsea infrastructure installed on the seabed

  • 16.
    Vahdati, Pooya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Levasseur, Séverine
    Département ArGEnCo Service de Géomécanique et géologie de l'ingénieur Université de Liège.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Inverse Hardening Soil Parameter Identification of an Earth and Rockfill Dam by Genetic Algorithm Optimization2014In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 19, no N, p. 3327-3349Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of identification of constitutive parameter values in the Hardening soil model by inverse analysis of an earth and rockfill dam application. The authors have experience from a previous study on the same case with the Mohr-Coulomb model. The objective of this research is to examine if the inverse analysis technique can be successfully used for this type of application and choice of constitutive model. The values of soil parameters are determined based on horizontal deformations obtained from installed instrumentations in the dam. The quantities that are monitored in the dam can be numerically predicted by a finite element simulation. In inverse analysis, constitutive parameter values are chosen in such a way that the error between data recorded by measurements in the dam and numerical simulation is minimized. An optimization method based on the genetic algorithm was applied to search for the minimum error in the search domain in this study. Optimizations have initially been performed in a large search domain in order to find a criterion identifying the best solutions. Thereafter, the optimizations were limited to this criterion in order to find the best set of solutions close to the optimum point. Moreover, the error function topology and smoothness was examined as well. It was overall concluded, that the inverse analysis technique could be effectively used for earth and rockfill dam applications, despite the fact that the technique is expensive in terms of computational time.

  • 17.
    Zardari, Muhammad Auchar
    et al.
    Department of Civil Engineering, MUET.
    Ormann, Linda
    Dam Safety Forum, Power Division Renewable Energy.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical Analysis of Staged Construction of an Upstream Tailings Dam2014In: Proceedings of 1st National Conference on Civil Engineering (NCCE 2013-14): (Modern Trends and Advancements), Quest Nawabshah, Pakistan: Department of Civil Engineering, Quest Nawabshah, Pakistan , 2014, p. 150-160Conference paper (Refereed)
    Abstract [en]

    A case study is presented in this paper which describes finite element analysis of staged construction of the upstream tailings dam Aitik, located in north of Sweden. The purpose of the study is to evaluate stability of the dam for current and future raisings and to strengthen the dam with optimum volume of rockfill banks on the downstream side when stability of the dam is not satisfactory during a construction stage. The finite element method was utilized to model the consolidation process and stability of the dam during the staged construction. The study has shown that stability of the dam during raisings was reduced due to build-up of excess pore pressures. Therefore, the dam was strengthened with rockfill banks on the downstream side to carry out the construction of the dam at a planned rate of raising. An optimization analysis was performed in order to reduce the volume of the rockfill necessary for stabilizing the dam. With the use of the finite element based optimization approach discussed in this paper, stability of the dams during staged construction can be enhanced by utilizing a minimum volume of rockfill banks.

  • 18.
    Makusa, Gregory Paul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shear strength evaluation of preloaded stabilized dredged sediments using CPT2014Conference paper (Refereed)
    Abstract [en]

    The undrained shear strength of preloaded stabilized dredged sediments increases with curing time. Evaluation of in-situ undrained shear strength using cone penetration test (CPT) data normally requires calibration of the CPT data with known undrained shear strength from vane shear test to obtain the cone factor, which is normally utilized in CPT empirical correlation to estimate the undrained shear strength. In this study, a new CPT empirical correlation for evaluation of in-situ undrained shear strength is presented. The proposed empirical correlation utilizes the effective vertical stress characteristic ratio to estimate the CPT induced stress, which was correlated to the in-situ undrained shear strength. The undrained shear strength computed using the proposed empirical correlation agrees reasonably well with the undrained shear strength estimated using the established empirical correlation at a large-scale field test.

  • 19.
    Vahdati, Pooya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Levasseur, Séverine
    Département ArGEnCo Service de Géomécanique et géologie de l'ingénieur Université de Liège.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Inverse Mohr-Coulomb soil parameter identification of an earth and rockfill dam by genetic algorithm optimization2013In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 18, no X, p. 5419-5440Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of identification of constitutive parameter values in the Mohr-Coulomb model by inverse analysis of an earth and rockfill dam application. The objective is to examine if the technique of inverse analysis can be effectively used for this type of case. The values of soil parameters are determined based on horizontal deformations recorded from installed instrumentations in the dam. The quantities that are monitored in the dam can be numerically predicted by a finite element simulation. In inverse analysis, constitutive parameter values are chosen in such a way that the error between data obtained by measurements in the dam and numerical simulation is minimized. An optimization method based on the genetic algorithm was utilized to search for the minimum error in this study. Optimizations have been performed against both a synthetic and a real dam case. The effect of the population size in the genetic algorithm was also analysed for this case in order to approach a proper set of solutions close to the optimum point by considering: the finite element computation time and the error function values. The error function topology was examined as well, and it was found to be complex and noisy for this application. The genetic algorithm is known to be a practically good choice of search method for such complicated topologies. It was overall concluded, that the inverse analysis technique studied, could be effectively used for this kind of earth and rockfill dam application despite the fact that, the technique is expensive in terms of computational costs. Inverse analysis has the potential to become a valuable tool for dam engineers assessing dam performance and dam safety if it becomes readily available in commercial finite element software.

  • 20.
    Vahdati, Pooya
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Levasseur, Séverine
    Université de Liège.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Inverse soil parameter identification of an earth and rockfill dam by genetic algorithm optimization2013Conference paper (Refereed)
    Abstract [en]

    The paper presents a study of constitutive parameter value identification by inverse analysis on an earth and rockfill dam application. The objective is to examine if the technique of inverse analysis can be effectively used for this type of case. In the inverse analysis procedure discussed here, values of constitutive parameters are determined based on data recorded from installed instrumentations in the dam. The quantities that are monitored in the dam can be numerically predicted by a finite element simulation. To perform a finite element simulation, constitutive models have to be chosen and values have to be assigned to the parameters included. In inverse analysis, constitutive parameter values are chosen in such a way that the error between data obtained by measurements in the dam and numerical simulation is minimized. This is accomplished by optimization. The genetic algorithm was utilized as the optimization strategy, to search for the minimum error, in this study. Optimizations have been performed both against a synthetic dam case and a real dam case. It was concluded, that the inverse analysis technique studied, could be effectively used for this kind of earth and rockfill dam application. However, the technique was time consuming. Inverse analysis has the potential to become a valuable tool for dam engineers assessing dam performance and dam safety if it becomes readily available in commercial finite element software.

  • 21.
    Makusa, Gregory Paul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Investigation of increased hydraulic conductivity of silty till subjected to freeze–thaw cycles2013In: no STP 1568, p. 33-46, article id STP156820120139Article in journal (Refereed)
    Abstract [en]

    The hydraulic conductivity of silty till increases when the till is subjected to freeze–thaw cycles. A dramatic increase normally occurs after the first freeze–thaw cycle, and the magnitude generally depends on the initial or molding water content. Freezing of silty till causes aggregations of clods and the formation of macrostructure. The initial or molding water content determines the number of freeze–thaw cycles required to complete the agglomeration of clods and the formation of stable macrostructures, which in turn controls the hydraulic conductivity of compacted specimens frozen and thawed in the laboratory. The findings of this study show that for specimens compacted wet of the optimum water content, a significant increase in the hydraulic conductivity was measured after the first freeze–thaw cycle. When specimens were compacted at the optimum water content, a number of freeze–thaw cycles were required in order to obtain the corresponding significant increase in the hydraulic conductivity.

  • 22.
    Ormann, Linda
    et al.
    Dam Safety Forum, Power Division Renewable Energy.
    Zardari, Muhammad Auchar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Bjelkevik, Annika
    Tailings Consultants Scandinavia AB.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical analysis of strengthening by rockfill embankments on an upstream tailings dam2013In: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 50, no 4, p. 391-399Article in journal (Refereed)
    Abstract [en]

    The consolidation process could be slow in an upstream tailings dam; therefore, the stability can reduce due to an increase in excess pore pressures when the dam is raised. The safety of the dam can be enhanced by constructing rockfill berms on the downstream side. This paper presents a case study on the strengthening of an upstream tailings dam with rockfill berms. The finite element analyses were performed for modelling the staged construction of the dam and for optimizing the volume of the rockfill berms. The dam was raised in 11 stages; each stage consisting of a raising phase and a consolidation phase. The study shows that the slope stability of the dam reduced due to an increase of excess pore pressures during the raising phase. The stability of the dam was successfully improved by utilizing rockfill berms as supports on the downstream side. A technique has been presented to minimize the volume of the rockfill berms so that the required stability can be achieved at minimum cost. This paper shows that the finite element method can be a useful tool for modelling the consolidation behaviour of an upstream tailings dam and minimizing the volume of the rockfill berms that may be needed to maintain the stability of the dam during staged construction.

  • 23.
    Auchar, Muhammad
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical modelling for stability of tailings dams2013Conference paper (Other academic)
    Abstract [en]

    A tailings dam is a large embankment structure that is constructed to store the waste from the mining industry. Stability problems may occur in a tailings dam due to factors such as quick rate of raising, internal erosion and liquefaction. The failure of a tailings dam may cause loss of human life and environmental degradation. Tailings Dams must not only be stable during the time the tailings storage facility is in operation, but also long time after the mine is closed. In Sweden, the licensing authorities demand that the tailings dams should be stable up to the next glaciation age, which is interpreted to be 1000 years or more. This goal requires extensive knowledge in order to be able to design the tailings dams so that they can be stable for such a long time. At the Division of Mining and Geotechnical Engineering at Luleå University of Technology, research has been conducted on the stability of tailings dams, using the finite element method which is considered to be suitable for modelling the complex geometry and the material properties of tailings dams. A case study is presented which describes the application of the finite element method in evaluating the stability of a tailings dam.

  • 24.
    Zardari, Muhammad Auchar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    3D finite element analyses of a corner at Aitik tailings dam in Sweden2012In: SWEMP 2012: International symposium on Environmental Issues and Waste Management in Energy and Mineral Production, 2012, p. 444-452Conference paper (Refereed)
    Abstract [en]

    The 3D finite element analyses were performed for the gradual raisings of a corner section of Aitik tailings dam, located in the north of Sweden. The purpose of the analyses was to investigate the potential risk of low compressive stresses or tensile stresses in the corner and to evaluate the slope stability of the dam for current and future raisings. The results indicate that the magnitudes of the minor effective principal stresses in the interior of the dam are sufficient to resist the development of soft zones or cracks in the dam and it is interpreted that there is no increased risk of internal erosion. The slope stability analyses show that the dam has enough safety up to a height of 76 m, if the dam is gradually strengthened with rockfill supports on the downstream side.

  • 25.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zardari, Muhammad Auchar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Ormann, Linda
    Sweco, Karlstad.
    Gruvdammar och deras stabilitet2012In: Bygg & Teknik, ISSN 0281-658X, Vol. 104, no 1, p. 49-52Article in journal (Other (popular science, discussion, etc.))
  • 26.
    Makusa, Gregory Paul
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Verification of field settlement of in-situ stabilized dredged sediments using cone penetration test data2012In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 17, no Y, p. 3665-3680Article in journal (Refereed)
    Abstract [en]

    Utilization of in-situ mass stabilization for geotechnical applications is increasing. Laboratory tests may have drawbacks on valuations of engineering parameters for estimations of settlement of in-situ stabilized soil mass. Factors such as compression, mixing work, homogeneity and curing temperature may influence the differences in mechanical properties between laboratory test results and achieved field values. Therefore, utilization of appropriate in-situ mechanical parameters may be required during design analyses. Various in-situ tests are available for use in geotechnical context. Among others, cone penetration test (CPT) is one of most widely used in-situ tests. Numerous CPT empirical correlations are available for use in conventional soils. Utilization of such CPT empirical correlations for in-situ stabilized soils has to be examined. In this paper, the in-situ constrained modulus was evaluated using conventional CPT empirical correlation and utilized as oedometer modulus in finite element analysis for estimation of settlement of preloaded in-situ stabilized dredged sediments. The results show that, computed settlement values fall within the range of measured one. These findings suggest that, the cone penetration test and its empirical correlations, which were established for conventional soils, can also be utilized in stabilized soils.

  • 27.
    Frishfelds, Vilnis
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fluid flow induced internal erosion within porous media: modelling of the no erosion filter test experiment2011In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 89, no 3, p. 441-457Article in journal (Refereed)
    Abstract [en]

    An investigation of the potential to numerically model the no erosion filter test is performed here, where the flow through a large ensemble of particles is considered by applying minimisation of dissipation rate of energy on the ensemble that is discretised with modified Voronoi diagrams and Delaunay triangulation. Low-Reynolds number simulations are applied to each part of the Voronoi diagram using computational fluid dynamics. The mechanical friction between particles is modelled by increasing the effective viscosity for closely spaced particles. Microscopic mechanisms for successful and unsuccessful sealing of filters are obtained. The numerical results agree with previously presented experimental observations by Sherard and Dunnigan. A conformity is that the sealing starts from the end of the channel and continues outwards in the radial direction. The sealing implies that the permeability can be reduced several orders of magnitude during a test.

  • 28.
    Ormann, Linda
    et al.
    Geotechnical Engineer, SWECO Infrastructure AB, Gjörwellsgatan 22, Stockholm.
    Zardari, Muhammad
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Bjelkevik, Annika
    Geotechnical Engineer, SWECO Infrastructure AB, Gjörwellsgatan 22, Stockholm.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical analysis of curved embankment of an upstream tailings dam2011In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 16, no I, p. 931-944Article in journal (Refereed)
    Abstract [en]

    A curved embankment (corner) of an upstream tailings dam was analyzed with the finite element method to identify possible zones of low compressive stresses susceptible to hydraulic fracturing that might initiate internal erosion. The embankment was also analyzed as a straight section, with the same cross section as in the corner, in order to compare compressive stresses in the corner and the straight section. The analysis showed that in comparison to the straight section of the dam, the compressive stresses in the corner were (i) much lower above the phreatic level, in the rockfill banks and the filter zones, and (ii) fairly lower below the phreatic level. The rockfill and the filter contain coarse materials, which are not sensitive to hydraulic fracturing and internal erosion. An increase in radius of the corner is proposed to avoid too low compressive stresses that may develop due to future raisings. The slope stability analysis showed that the corner is currently stable, but an additional rock fill bank on the downstream toe is required for future raisings.

  • 29. Frishfelds, Vilnis
    et al.
    Hellström, J. Gunnar I.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fluid flow induced deformation of porous medium: modeling of the no erosion filter test experiment2010In: Proceedings of the 3rd International Conference on Porous Media and its Applications in Science and Engineering: ICPM3, 2010Conference paper (Refereed)
    Abstract [en]

    To study internal erosion in depth it is necessary to know either the detailed flow or how it varies in a statistical manner. It is also important to know how the internal erosion process initiates and progresses due to the fluid flow-induced forces. The underlying reason for this is that internal erosion will initiate exactly where the forces from the fluid are higher than the retaining forces that keep the particles together. Hence, a new model is here developed where fluid flow induced deformations of a large number of particles is studied. The model is applied to the No Erosion Filter test and simulated results resemble experimental results from the literature. The NEF test is used to investigate parameters such as the hydraulic conductivity and also in detail the process of internal erosion. The simulations are performed on different set-ups to exemplify successful and unsuccessful sealing. In the model, minimization of the dissipation rate of energy is accompanied with discretization of the system with modified Voronoi diagrams. Then Computational Fluid Dynamics is applied to solve the flow within each part of the Voronoi diagrams. Different parameters, such as the vorticity, calculated with the CFD-software are then used as input to the Monte Carlo-simulations. An overall good conformity between simulated results and experimental results from the literature is obtained.

  • 30.
    Knutsson, Sven
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hellström, Gunnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Project: Internal erosion in embankment dams2010Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Since older embankment dams have a tendency to gradually display an increased degree of leakage it is interesting to find out if this phenomenon can be captured by an inverse modelling approach. Numerical tests with a model system will hopefully lead to a better understanding of the decomposition of material in dams and enhance the knowledge about the long term effects in order to forsee potential problems in the future.These embankment dams typically consist of a central core of moraine that is surrounded by a filter, a transition layer and a fill material. Ideally the seepage through the dam is relatively small and the effect on the dam from the flow is negligible. However, in reality there are several situations that promote a fatal failure of the dam including overtopping at high flood discharges, internal erosion and seepage problems in the embankment and the foundation. The status of embankment dams are generally examined by in-situ measurement of one or several of the following quantities: pore pressure, inclination and settlement, temperature, resistivity, self-potential, seepage rate, turbidity of the seepage water, ground penetration radar and bore hole tomography. These indirect and/or discrete methods give indication of the condition of the dam leaving the real situation for the imagination. Hence, when there are alterations to measured values great efforts are often spent on reinforcing dams in order to keep a high safety level. An increased knowledge of the composition of material in dams would enable the usage of focused measures reducing the costs and increasing the safety.

  • 31.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    On numerical modelling of internal erosion in embankment dams2009In: Proceedings 1st International Symposium on Rockfill Dams: October 18-21, 2009, Chengdu, China, 2009Conference paper (Refereed)
  • 32.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hellström, J. Gunnar I.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    On internal erosion in embankment dams: a literature survey of the phenomenon and the prospect to model it numerically2008Report (Other academic)
    Abstract [en]

    The main objective with this literature survey is to elucidate the state of the art of internal erosion in embankment dams in order to be able to formulate a research program for numerical modelling of internal erosion in a physically sound manner. Since these processes normally are localised to specific zones in a dam, the ordinary continuum approach frequently utilised in soil modelling will not, by itself, be successful. The plan of the research group is therefore to treat internal erosion numerically as a type of localisation and describe the constitutive behaviour with micromechanical models in localised zones. In the next step, the internal erosion model developed will be implemented in a mathematical consistent fashion in a continuum model, based on e.g. the finite element method. In such software, ordinary computations of stresses, strains, deformations and pore pressures in an embankment dam can be performed; results which possible lead to conclusions about the initiation of internal erosion processes. When internal erosion is initiated, the micromechanical models will describe these processes in localised zones. It was decided to restrict the literature survey to areas important for the research direction defined above. The chosen areas are thus: numerical modelling of embankment dams, internal erosion processes, embankment dam failures and accidents, filter design, micromechanical models of hydro dynamical loads on single particles and system of particles as well as micromechanical models for friction between single grains and system of grains. The most essential findings for each area, in the context of the research, will be described below. There exists much experience in the field numerical modelling of embankment dams which is exemplified by the large amount of published papers on the subject. However, the processes of internal erosion have not been modelled in a general manner, as outlined in the research idea above, in any of the papers cited in this literature survey. There are three main internal erosion processes that can initiate piping: backward erosion, concentrated leak and suffusion. Piping can occur in the embankment, through the foundation and from the embankment into the foundation. Embankment dams are normally constructed in zones of different materials. Different compressibilities of the various zones might lead to internal redistribution of stresses and uneven settlements, which might cause cracks or "soft zones" where internal erosion can be initiated. Cracks can also occur later on by hydraulic fracturing. All of that described above are examples of mechanical processes that are theoretically possible to model numerically. To receive information about potential internal erosion problems in a dam at an early stage, geophysical methods are a promising alternative or complement to numerical methods. However, much research and development remain before the results from geophysical methods utilised for permanent monitoring and surveillance of dam structures are completely trustful. It is often very difficult to determine the exact reason for a dam accident or a failure since the processes involved have a tendency to destroy evidence which might have existed. Statistical data, however, shows that failure by overtopping and piping are the most common modes of failure while failure by slides is less common. Many piping failures occur very fast, leaving a short time for proper actions. The safety of large embankment dams is strongly dependent on the reliability of the performance of their critical filters. Existing filter design criteria are in most cases empirically derived, implying that a lot of knowledge can be gained by taking a mechanical approach to the problem. More research would also be desirable in the field of ageing effects of dams and uncertainties of core/filter appearance during and after accidents, incidents etc. For this, numerical modelling also seems to be a promising approach. Continuum formulations of flow through porous media often results in equations consisting of a few unknown parameters such as the permeability. The physical background of such parameters can often be traced to the detailed flow in the pores and it is therefore in place to study the flow on this level, as well. The forces on individual particles have been exploited for certain geometries and for a number of flow conditions. We however need to investigate further higher Reynolds number flows, more complex geometries and instationary conditions. The forces from the micromechanical models must be balanced by gravity and forces that emanates from particle interactions for the dam to be stable. As a first, and most simple, criteria the size distribution of the particles being subjected to hydrodynamic pressure is compared to the pore size distribution of the porous medium. Hence the particles will move if they are small enough independent on magnitude of the force on it. In reality, however, the hydraulic forces must exceed particle interaction forces and or gravitational forces keeping the particles in place at normal conditions. The forces are strongly dependent on the size of the particles and therefore dependent on different phenomena such as cohesion, adhesion and static friction. In the final part of the literature survey a concept for numerical modelling of internal erosion is presented based on ideas that have emerged from this work. The concept involves as well mathematical developments in order to formulate a micromechanical model for internal erosion as laboratory tests. The theoretical work and the practical laboratory work should be performed simultaneously and in an interactive manner. A software containing a model that simulates internal erosion could be useful for: an increase of the knowledge about internal erosion processes, evaluating the risk for dam incidents caused by internal erosion, estimating the time for progression of internal erosion and piping, studying self-healing of leaks, changes in filter behaviour subsequent to particle accumulation and ageing effects in dams, analysing the amount of instrumentation needed in a dam and the proper location for monitoring and surveillance as well as designing dams to mention a few examples. It is therefore apparent that the route suggested has a high potential to become a tool for future improvements of dam safety.

  • 33.
    Hellström, J. Gunnar I.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Fluid mechanics of internal erosion in embankment dams2007In: Parallel computing of fluid flow through porous media, Luleå: Luleå tekniska universitet, 2007Chapter in book (Other academic)
  • 34.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Klisinski, M.
    Axelsson, Kennet
    Luleå University of Technology.
    Optimization routine for identification of model parameters in soil plasticity2001In: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 25, no 5, p. 435-472Article in journal (Refereed)
    Abstract [en]

    The paper presents an optimization routine especially developed for the identification of model parameters in soil plasticity on the basis of different soil tests. Main focus is put on the mathematical aspects and the experience from application of this optimization routine. Mathematically, for the optimization, an objective function and a search strategy are needed. Some alternative expressions for the objective function are formulated. They capture the overall soil behaviour and can be used in a simultaneous optimization against several laboratory tests. Two different search strategies, Rosenbrock's method and the Simplex method, both belonging to the category of direct search methods, are utilized in the routine. Direct search methods have generally proved to be reliable and their relative simplicity make them quite easy to program into workable codes. The Rosenbrock and simplex methods are modified to make the search strategies as efficient and user-friendly as possible for the type of optimization problem addressed here. Since these search strategies are of a heuristic nature, which makes it difficult (or even impossible) to analyse their performance in a theoretical way, representative optimization examples against both simulated experimental results as well as performed triaxial tests are presented to show the efficiency of the optimization routine. From these examples, it has been concluded that the optimization routine is able to locate a minimum with a good accuracy, fast enough to be a very useful tool for identification of model parameters in soil plasticity.

  • 35.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Klisinski, Marek
    Optimeringsrutin för bestämning av modellparametrar2000In: Proceedings of the 13th Nordic Geotechnical Conference, NGM 2000: Helsinki, Finnish Geotechnical Society / [ed] Hans Rathmayer, Helsinki: Building Information Ltd , 2000, p. 33-40Conference paper (Refereed)
  • 36.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Luleå University of Technology.
    Klisinski, M.
    Luleå University of Technology.
    On a constitutive driver as a useful tool in soil plasticity1999In: Advances in Engineering Software, ISSN 0965-9978, E-ISSN 1873-5339, Vol. 30, no 8, p. 511-528Article in journal (Refereed)
    Abstract [en]

    A mathematical basis for the development of constitutive drivers in soil plasticity has been proposed by the authors. A constitutive driver is here understood as a computer program, containing a number of selected constitutive models, in which different laboratory and field tests can be simulated and model parameters optimised. As a pilot study of the mathematical concept, a constitutive driver for soils, in the form of a PC-program, has been developed. The paper discusses this particular program, i.e. its structure, the mathematical basis, included soil models and some application examples, to give an idea of how a general and user-friendly constitutive driver can be designed. Such a program can be used for practical, research and educational purposes. In fact, it is believed that so many important applications for constitutive drivers exist that it would be beneficial if such programs were easily accessible as complementary programs in commercial software.

  • 37.
    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.

  • 38.
    Sheng, Daichao
    et al.
    Luleå University of Technology.
    Westerberg, Bo
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Luleå University of Technology.
    Effects of end restraint and strain rate in triaxial tests1997In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 21, no 3, p. 163-182Article in journal (Refereed)
    Abstract [en]

    Inhomogeneities caused by end restraint and insufficient drainage during conventional compression triaxial tests are analysed by a numerical method. A finite element model is presented to simulate the testing procedure. The soil-platen interaction is represented by contact elements which allow frictional sliding between contacting nodes. The soil mass is represented by the modified Cam clay model. Coupled hydro-mechanical analyses are carried out in order to simulate both drained and undrained tests. The distributions of stresses and strains in the specimen for different end conditions are compared with the ideal case where no end restraint exists, in order to find representative measuring positions in the sample. Different rates of axial strain are tested in order to study the inhomogeneities caused by insufficient drainage during drained tests. Simulated results show that both end restraint and insufficient drainage can cause the barrel-shape deformation of the specimen. Stress-strain and strength properties based on global measurements are not a good representation of the true material behaviour of one single soil element at constitutive level.

  • 39.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Luleå University of Technology.
    Klisinski, Marek
    Luleå University of Technology.
    Method to correct yield surface drift in soil plasticity under mixed control and explicit integration1997In: International journal for numerical and analytical methods in geomechanics (Print), ISSN 0363-9061, E-ISSN 1096-9853, Vol. 21, no 3, p. 175-197Article in journal (Refereed)
    Abstract [en]

    When applying an explicit integration algorithm in e.g. soil plasticity, the predicted stress point at the end of an elastoplastic increment of loading might not be situated on the updated current yield surface. This so-called yield surface drift could generally be held under control by using small integration steps. Another possibility, when circumstances might demand larger steps, is to adopt a drift correction method. In this paper, a drift correction method for mixed control in soil plasticity, under drained as well as undrained conditions, is proposed. By simulating triaxial tests in a Constitutive Driver, the capability and efficiency of this correction method, under different choices of implementation, have been analysed. It was concluded that the proposed drift correction method, for quite marginal additional computational cost, was able to correct successfully for yield surface drift giving results in close agreement to those obtained with a very large number of integration steps.

  • 40. Sheng, Daichao
    et al.
    Westerberg, Bo
    Mattsson, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Numerical analysis of stress-strain inhomogeneities in a triaxial test specimen1997In: Proceedings of the Fourteenth International Conference on Soil Mechanics and Foundation Engineering: Hamburg, 6 - 12 September 1997, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1997, p. 403-407Conference paper (Refereed)
  • 41.
    Mattsson, Hans
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Axelsson, Kennet
    Konstitutiv drivenhet för simulering av jordars beteende1996In: Proceedings XII Nordic Geotechnical Conference / [ed] S. Erlingsson; H. Sigursteinsson, Icelandic Geotechnical Society , 1996, p. 49-59Conference paper (Refereed)
1 - 41 of 41
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