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  • 1.
    Edelbro, Catrin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical modelling of observed fallouts in hard rock masses using an instantaneous cohesion-softening friction-hardening model2009Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 24, nr 4, s. 398-409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The work presented in this paper focuses on compressive stress-induced brittle fallouts in hard rock masses, which are massive or sparsely fractured and subjected to intermediate to high in situ stresses. The results of numerical modelling, using a linear-elastic, brittle plastic material model with cohesion-softening friction-hardening (CSFH) behaviour, were compared with observed fallouts for six cases. The objective was to study how well the results of a CSFH model agrees with observed fallouts with respect to location, depth, and shape. All six cases were well documented with respect to virgin stresses, fallout characteristics, rock mass properties, and rock behaviour. The modelling results showed that shear strain localization (shear bands) developed for all cases. The depth of the intersected shear bands were used as a fallout indicator. Furthermore, the location and shape of the observed fallouts could be predicted fairly accurately. The predicted fallout depth was in good agreement with observed fallouts for three of the cases. Using both yielded elements and intersecting shear bands as fallout indicators results in a better prediction of fallout than using just one indicator.

  • 2.
    Edelbro, Catrin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Sjöberg, Jonny
    Nordlund, Erling
    A quantitative comparison of strength criteria for hard rock masses2007Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 22, nr 1, s. 57-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of the rock mass strength is important for the design of all types of underground excavations. A frequently applied approach for estimation of the rock mass strength is through an empirical failure criterion, often in conjunction with rock mass classification/characterisation systems. This paper presents a review of existing methods to estimate the rock mass strength using empirical failure criteria and classification/characterisation systems—in this study, commonly denoted as estimation methods. A literature review of existing methods is presented, after which a set of methods were selected for further studies. The selected methods were used in three case studies, to investigate their robustness and quantitatively compare the advantages and disadvantages of each method. A Round Robin test was used in two of the cases. The case studies revealed that the N, Yudhbir-RMR76, RMi, Q-, and Hoek–Brown-GSI methods, appeared to yield a reasonable agreement with the measured strengths. These methods are thus considered the best candidates for realistic strength estimation, provided that care is taken when choosing values for each of the included parameters in each method. This study has also clearly shown the limits of presently available strength estimation methods for rock masses and further work is required to develop more precise, practical, and easy-to-use methods for determining the rock mass strength. This should be based on the mechanical behaviour and characteristics of the rock mass, which implies that parameters that consider the strength of intact rock, block size and shape, joint strength, and physical scale, are required.

  • 3.
    Hatem, Mohammed
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Pusch, Roland
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Study of cement-grout penetration into fractures under static and oscillatory conditions2015Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 45, s. 10-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Grouting of the rock surrounding high-level waste (HLW) can serve to minimize groundwater flow around it and thereby to retard erosion of waste-embedding clay (buffer) and transport of possibly released radionuclides. Earlier attempts have shown the efficiency of superimposing the injection pressure with oscillations for bringing cement-rich grouts into narrow fractures using organic superplasticizers. However, these are short-lived and can produce radionuclide-bearing organic colloids, and should be replaced by inorganic agents. Portland cement in grouts is not long lived and low-pH cements are preferable as is also reduction of the cement content to an absolute minimum. The present study describes the composition and performance of candidate grouts in laboratory experiments with injection into plane-parallel slots with different aperture. The study included development of a simple and quick method for estimating the viscosity on the construction site for adapting the grout recipe to the injectability of the rock. A simple theoretical model for predicting grout penetration gives fair agreement with laboratory data. The longevity of the grout under various conditions is believed to be sufficient for use in HLW repositories implying waste placement in very deep holes

  • 4.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stochastic assessment of pillar stability at Laisvall mine using Artificial Neural Network2015Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 49, s. 307-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Stability analyses of any excavations within the rock mass require reliable geotechnical input parameters such as in situ stress field, rock mass strength and deformation modulus. These parameters are intrinsically uncertain and their precise values are never known, hence, their variability must be properly accounted for in the stability analyses. Traditional deterministic approaches do not quantitatively consider these uncertainties and variability in the input parameters. To incorporate these variability and uncertainties stochastic approaches are generally used. In this study, a stochastic assessment of pillar stability using Artificial Neural Network (ANN) is presented. The variability and uncertainty in the rock mass properties at the Laisvall mine were quantified and the probability density function of the deformation modulus of the rock mass was determined using probabilistic approach. The variability of the in situ stress was also considered. The random values of the deformation modulus and the horizontal in situ stresses were used as input parameters in the FLAC3D numerical simulations to determine the axial strain in the pillar. ANN model was developed to approximate an implicit relationship between the deformation modulus, horizontal in situ stresses and the axial strain occurring in pillar due to mining activities. The closed-form relationship generated from the trained ANN model, together with the maximum strain that the pillar can withstand was used to assess the stability of the pillar in terms of reliability index and probability of failure. The results from this study indicate that, the thickness of the overburden and pillar dimension have a substantial effect on the probability of failure and reliability index. Also shown is the significant influence of coefficient of variation (COV) of the random variables on the pillar stability. The approach presented in this study can be used to determine the optimal pillar dimensions based on the minimum acceptable risk of pillar failure

  • 5.
    Ittner, Henrik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi. Svensk Kärnbränslehantering AB.
    Olsson, Mats
    EDZ Consulting AB.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Multivariate evaluation of blast damage from emulsion explosives in tunnels excavated in crystalline rock2019Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 85, s. 331-339Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blast damage in tunnels is usually regulated in Swedish infrastructure contracts as it can influence the quality and lifecycle cost for tunneling projects. The topic is important for underground constructions with a long operation period such as tunnels for public transport, permanent access tunnels in mines or underground repositories for nuclear waste. This paper aims to evaluate the influence of design and geology variables on the resulting blast fracture length and frequency by means of multivariate data analysis. The analysis was based on data from five field investigations carried out at tunnel sites in Sweden and Finland where emulsion explosives were used. Data was compiled and analyzed using Principal Component Analysis (PCA). Charge concentration was found to be the most influential design variable and hole spacing had limited influence on blast fracturing. Results from the PCA suggest that blast fractures length could be dependent also on geology and natural fractures. Three main groups of fracture patterns were identified, one group with relatively few and short blast fractures, a group with several longer blast fractures and a group with few or a single long blast fracture. The result shows differences in fracture length between the column and bottom charge part of the contour holes, with blast fracture lengths up to approx. 40 cm for the column charge and up to approx. 60 cm for the bottom charge.

  • 6. Malmgren, Lars
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rolund, S.
    WSP, Malmberget.
    Adhesion strength and shrinkage of shotcrete2005Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 20, nr 1, s. 33-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shotcrete is widely used as rock support in mines and in civil engineering projects. In many cases the adhesion between the shotcrete and the rock is one of the most important properties. The objective of this study was to: (i) identify typical failures of shotcrete in a mining environment, (ii) measure the growth of the adhesion strength of shotcrete with respect to age, (iii) investigate the influence of surface treatment (scaling and cleaning) on the adhesion strength of shotcrete and (iv) investigate the occurrence of shrinkage cracks in the shotcrete and failures in the interface between the shotcrete and the rock. The failure mapping showed that most of the observed failures of shotcrete are in areas with a thin shotcrete layer ( less than or equal 20 mm) together with a low adhesion strength. Furthermore, the measured average thickness of shotcrete (40 mm) was almost the same as the ordered thickness, the problem is the wide scatter. In 18% of the thickness measurements, the shotcrete thickness was less than or equal to 20 mm. If the shotcrete lining in the mine has the same thickness distribution as during the tests, the supporting ability of as much as 18% of the shotcrete lining can be considered as more or less negligible. No differences in free shrinkage were observed between plain and steel fibre reinforced shotcrete. Relatively large areas with lack of contact between shotcrete and wall were observed in the shrinkage tests. This indicates that restrained shrinkage can destroy the bond between the shotcrete and rock. The results from the restrained shrinkage tests show the importance of the bond at the interface. If bond failure occurs, the ability to distribute and control the crack width ceases. The growth of the adhesion strength on a sandblasted concrete wall and the growth of the compressive strength showed a correlation. However, the scatter in the results indicates that further investigations have to be done in order to establish a reliable relation between the growth in adhesion and compressive strength with age. The results from the field tests showed that the adhesion strength was significantly higher on rock surfaces that had been water jet-scaled (with 22 MPa water pressure) than those treated by mechanical scaling followed by cleaning of the rock surface (water pressure 0.7 MPa).

  • 7.
    Nordell, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    The borehole heat store in rock at the Lulea University of Technology: constructional and operational experience : The Lulevärme Project 1982-19851988Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 3, nr 1, s. 85-Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Constructional work on the borehole heat store in Lulea was started in August 1982, and the store was started up in July 1983. The work was carried out on a turnkey basis by Svenska Energi System AB (SES), Lulea. The objective of the project is to demonstrate and investigate borehole heat storage technology in this experimental heat store. The actual heat store itself consists of a volume of rock amounting to about 100,000 m**3, beneath an overburden of mineral soil 2-6 m in depth. 120 boreholes have been drilled in the bedrock to a depth of 65 m, and serve as heat exchangers when charging and discharging the store. Much of the research program involves measurements intended to document performance of the store.

  • 8.
    Nordell, Bo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Bjarnholt, Gjert
    Swedish Detonic Research Foundation, Luleå.
    Stephansson, Ove
    Luleå tekniska universitet.
    Torikka, Arne
    Luleå tekniska universitet.
    Fracturing of a pilot plant for borehole heat storage in rock1986Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 1, nr 2, s. 195-208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes research on a pilot plant in Luleå, Sweden. The plant consists of 19 boreholes, 52 mm in diameter, for heat supply and extraction; and 10 boreholes for temperature monitoring. All the boreholes are 21 m deep. The report describes in detail the performance and results of rock mass permeability and borehole permeability tests. It also discusses hydraulic fracturing and explosive fracturing in the boreholes. A simulation model of water flow in the test plant is described. The paper includes conclusions from the test results and recommendations for further study.

  • 9.
    Nordell, Bo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Hallberg, Rolf O.
    Sjöberg, Lennart
    Leaching of rock fractures: Laboratory and field tests for borehole heat stores1989Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 4, nr 1, s. 99-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this research project was to increase the hydraulic conductivity of fractured rock by pumping a leaching fluid (NaOH) through rock fractures. A 16-week field test was carried out in a borehole heat store consisting of 19 vertical boreholes to a depth of 15 m in gneissic rock. The leaching process was studied simultaneously in a laboratory test where rock samples from core drillings of the test site were used. The hypothesis that NaOH-solution would leach and thereby widen the fractuers, was not fulfilled. On the contrary, the fractures were sealed as the leaching test went on. The explanation for this is that the leaching rate was higher than expected, the leaching fluid was saturated and the dissolved minerals precipitated. In principle, the minerals were dissolved and moved from one part of the fractures to precipitate at another part, causing clogging. The effect of the leaching field test has been simulated by means of a numerical model. The conclusion is that a leaching of rock as described in this paper should be combined with a deposition tank for the clogging material in order to avoid precipitation in the rock fractures. The results of this project have demonstrated a way of sealing rock fractures that has many more applications in engineering geology.

  • 10.
    Nordell, Bo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Ritola, Jouko
    Sipilä, Kari
    Sellberg, Björn
    The combi heat store - a combined rock cavern/borehole heat store1994Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 9, nr 2, s. 243-249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since 1988, Sweden and Finland have collaborated bilaterally on thermal energy storage with respect to information exchange and collaborative R&D projects. The two countries have both investigated underground thermal energy storage for nearly two decades, and have similar bedrock-the Fenno-Scandian granitic rocks. This paper reviews the work performed in the field of combined rock cavern and borehole heat stores, concerned with construction technology, costs and design principles. One example is an asymmetric store, in the form of 40- to 60-m-long horizontal boreholes between two rock caverns, with the caverns themselves comprising only about 10% of the total storage volume. This design has a specific cost of $US0.40 million/ GWh and $US0.24 million/ GWh for storage capacities of 6 GWh and 36 GWh, respectively. Half of the total construction cost relates to the rock cavern part of the store.

  • 11.
    Pérez, Kelvis
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Failure process analysis of spalling failure: comparison of laboratory test and numerical modelling data2012Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 32, s. 66-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a comparison of laboratory tests and numerical modelling results for evaluation of spalling failure in hard rock. The aim of this paper was to evaluate if the failure and deformation (i.e., strain at crack initiation, crack damage and peak strength stages) process in the zone of spalling failure of two real excavations can be predicted by using strain data from rocks tested in laboratory. Data such as axial strain and lateral strain quantities from uniaxial compressive laboratory test performed on Fennoscandian hard rocks were used. Numerical modelling of these excavations using Phase2 was conducted. Volumetric strain and maximum shear strain were chosen as indicators of the depth and shape of the spalling failure developing in the walls and roof of the excavations. Quantities within the spalling failure zone such as volumetric strain, maximum shear strain, and major and minor principal strain, were calculated, and compared to the failure-deformation data of limestone and quartzite (from laboratory tests). This paper shows that the failure process of hard rock excavations can be predicted by using laboratory test data. This paper further demonstrated that the onset of cracking calculated from laboratory tests can be related to the in situ crack initiation strain.

  • 12. Sagefors, I.
    et al.
    Daerga, Per-Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    An excavation method for large vertical cylindrical caverns1996Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 11, nr 3, s. 279-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Construction of underground storage chambers in rock has traditionally adopted a construction-oriented approach; the cavern design and the method of excavation have been governed by the capabilities of the equipment available. One example is oil storage in unlined horizontal caverns. Today, however, equipment is no longer a limiting factor. The time has come to integrate the construction and operational aspects in the design process. This paper presents a construction concept developed for large vertical rock caverns with a circular or elliptical horizontal cross-section. The method of excavation, called PBM (Pillar Blasting Method), is condensed into a few main operations which are geometrically separated but overlapping in time. PBM is characterized by two main working sites per cavern, and by long-hole bench-drilling, massive blasting rounds, continuous loading and easy ventilation. Recent developments in drilling and blasting techniques are incorporated, such as the water-driven in-the-hole hammer and the electronic ignition system. PBM enables a high rate of excavation and provides a satisfactory working environment with respect to labour safety and human health (a limited exposure to large openings, no exposure to oil mist and to combustion and explosive fumes, etc). Considerable construction cost savings and time savings may thus be achieved compared to conventional methods of excavation for vertical and horizontal caverns of equal storage volume. A preliminary PCT patent (application No PCT/SE95/00324) has been granted. Examples of applications are fresh-water reservoirs, natural gas reservoirs, subsurface hydroelectric pump power plants, and similar objects which require a large underground storage space in preferably unlined rock caverns.

  • 13.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    RQD predictions based on drill performance parameters1996Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 11, nr 3, s. 345-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In tunnelling and in other underground constructions, a detailed knowledge of the rock mass to be excavated is essential for reasons of safety, reinforcement need and cost and time schedule for the excavation. This paper presents a new approach to how drill performance parameters can be used for rock quality designation (RQD) prediction. Predictions are based not only on traditional parameters as penetration rate and torque, but also on the variability of each parameter which shows a close correlation to fracturing. Since predictions are based on drill monitoring data with high resolution, the prediction can provide detailed information of the structural geometry of the rock mass ahead of the operation. Examples are given from a railway tunnel in northern Sweden built in granitic bed-rock

  • 14.
    Shirzadegan, Shahin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Large scale dynamic testing of rock support at Kiirunavaara: Improved test design2016Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 59, s. 183-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on the test results and preliminary numerical analysis of four large scale dynamic testing of rock support (Tests 1, 2, 4, and 5), a modified test (Test 6) was designed at LKAB Kiirunavaara underground mine. The aim of the modified design was to avoid the unexpected damage of burden as was observed in earlier tests, and to modify the dynamic loading leading to increase the depth of fractured zone and if possible pushing the support system beyond its limit. In this test, ground motion measurements were conducted using accelerometers, fracture investigations were made using an inspection borehole camera, and ground motion imaging and laser scanning were performed before and after blast. In Test 6, the columns of explosive were located in the middle of a pillar between two cross-cuts one supported by a rock support for seismic conditions, and the other supported by only plain shotcrete. Results indicated that a larger fractured zone compare to earlier tests was developed behind the support system while the installed support system was still functional. In cross-cut without support system, the ejection of blocks of rock from the test wall was observed. Evidence from two cross-cuts indicated a reduction of radial cracks that provide access for the gas expansion. Furthermore, the performance of the rock support was investigated by comparing with the results from the unsupported cross-cut. The results indicated that the installed support system, designed for dynamic conditions, performed well under the loading conditions which can cause ejection.

  • 15.
    Tuomas, Göran
    Luleå tekniska universitet.
    Effective use of water in a system for water driven hammer drilling2004Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 19, nr 1, s. 69-78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Drilling with water driven down-the-hole (DTH) hammers is a recently developed method for competitive production of boreholes. In order to prevent large amounts of water being used during operation, the drilling fluid is here directly processed into a quality acceptable for reuse. The effectiveness is evaluated in well drilling with a mobile prototype water cleaning and pressurising unit. Especially the presence of abrasive particles in the fluid can drastically reduce tool life and make the method inefficient. The vital significance of this relation has called for detailed studies and a process simulation model for determining particle concentration and size distribution has been developed. This paper describes the model and how it is applied. Simulation results of different system configurations are also presented

  • 16.
    Yi, Changping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Lu, Wenbo
    Rock Mechanics in Hydraulic Structural Engineering, Ministry of Education.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nyberg, Ulf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effect of imperfect interface on the dynamic response of a circular lined tunnel impacted by plane P-waves2016Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 51, s. 68-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A theoretical method for studying the dynamic response of a circular lined tunnel with an imperfectly bonded interface subjected to plane P-waves is presented in the paper. The wave function expansion method was used and the imperfect interface was modeled with a spring model. Two cases were discussed in the paper. In the first case rock is harder than the lining and vice-versa in the second case. The results indicated that the variation in the stiffness of the interface has much influence on the distribution of dynamic stress concentration factors (DSCF) in the rock and the lining. The imperfection of the interface has a more noticeable influence on the DSCF in the rock mass and the lining at high frequency incident wave's scenario than low frequency incident wave's scenario. The resonance scattering phenomena can be observed when the bond is extremely weak. Limiting cases were considered and a good agreement with the solutions available in the literature was obtained.

  • 17.
    Yi, Changping
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Sjöberg, Jonny
    Itasca Consultants AB.
    Johansson, Daniel
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical modelling for blast-induced fragmentation in sublevel caving mines2017Ingår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 68, s. 167-173Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow behavior of the ore and waste significantly affect the dilution in sublevel caving (SLC) mines. Drill and blast issues are identified as having a substantial impact upon SLC material flow. In the paper, blast-induced fragmentation in SLC was numerically investigated using the LS-DYNA code. A method was presented to evaluate fragmentation based on the damage description and a fragment identification routine implemented in the LS-PREPOST (a pre- and post-processing tool of LS-DYNA). The effects of the delay time and the primer position on fragmentation were investigated. The results indicated that a long delay time gives a finer fragmentation for the cases discussed in the paper. The results also showed that the middle primer and the top primer in SLC can give a fine fragmentation. The limitations of numerical modelling were also discussed.

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