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  • 1.
    Barba, Tomas Villegas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical analyses of the hangingwall failure due to sublevel caving: study case2013Inngår i: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 4, nr 3, s. 201-223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sublevel caving used in Kiirunavaara mine induces failure and subsidence of the hangingwall. Two sections of the mine were studied by means of numerical analyses. Numerical models were developed using finite element and discrete element codes. The former was applied to calculate the location of new failure surfaces in the hangingwall and to estimate the break angle when mining advances downwards. The latter was used to analyse the displacement path of the caved rock during draw and to determine its effect on the stability of the hangingwall and footwall. The models were calibrated using displacement monitoring data. The finite element analyses indicated that the break angle is almost constant for deeper mining levels but may change if the geometry of the orebody changes. The discrete element model showed the formation of a stationary zone along the footwall that reduces the magnitude of the shear forces during draw, increasing its stability.

  • 2. Bondarchuk, Alexander
    et al.
    Ask, Maria
    Dahlström, Lars-Olof
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical analysis of rock mass behavior under hydropower embankment dams2009Inngår i: Föredrag vid Bergmekanikdag i Stockholm 9 mars 2009, Stiftelsen bergteknisk forskning - Befo , 2009, s. 149-158Konferansepaper (Annet vitenskapelig)
    Abstract [sv]

    Numeriska analyser av bergmassans beteende under fyllningsdammar för vattenkraftproduktion

  • 3.
    Bondarchuk, Alexander
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Dahlström, Lars-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rock mass behavior under hydropower embankment dams: a two-dimensional numerical study2012Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 45, nr 5, s. 819-835Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sweden has more than 190 large hydropower dams, of which about 50 are pure embankment dams and over 100 are concrete/embankment dams. This paper presents results from conceptual analyses of the response of typical Swedish rock mass to the construction of a hydropower embankment dam and its first stages of operation. The aim is to identify locations and magnitudes of displacements that are occurring in the rock foundation and grout curtain after construction of the dam, the first filling of its water reservoir, and after one seasonal variation of the water table. Coupled hydro-mechanical analysis was conducted using the two-dimensional distinct element program UDEC. Series of the simulations have been performed and the results show that the first filling of the reservoir and variation of water table induce largest magnitudes of displacement, with the greatest values obtained from the two models with high differential horizontal stresses and smallest spacing of sub-vertical fractures. These results may help identifying the condition of the dam foundation and contribute to the development of proper maintenance measures, which guarantee the safety and functionality of the dam. Additionally, newly developed dams may use these results for the estimation of the possible response of the rock foundation to the construction

  • 4. Bondarchuk, Alexander
    et al.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dahlström, Lars-Olof
    Nordlund, Erling
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Hydromechanical numerical analysis of rock mass behavior under a Swedish embankment hydropower dam2009Inngår i: Long Term Behaviour of Dams: Proceedings of the 2nd International Conference, 12th-13th October 2009, Graz, Austria / [ed] Erich Bauer; Stephan Semprich; Gerald Zenz, Graz: Verl. der Techn. Univ. Graz , 2009, s. 113-118Konferansepaper (Fagfellevurdert)
  • 5. Carlsson, B.
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Andersson, Y.
    Lindfors, U.
    The failure process and the acoustic emission of brittle rock under compression1999Inngår i: 9 Congres international de mecanique des roches : comptes-rendus : Paris, France, 1999 / [ed] Gérard Vouille, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1999, s. 569-572Konferansepaper (Fagfellevurdert)
  • 6.
    Chen, Guanghui
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Li, Xibing
    School of Resource and Safety Engineering, Central South University, Changsha, Hunan.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dong, Longjun
    School of Resource and Safety Engineering, Central South University, Changsha, Hunan.
    Optimization of tunnel support parameters with consideration of seismic wave radiation pattern in the fault-slip burst2017Inngår i: Journal of Mining and Safety Engineering, ISSN 1673-3363, Vol. 34, nr 4, s. 715-722Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As the underground mining extends gradually towards depth, more and more seismic events induced by fault slip occur and cause great damages, which have become a severe potential threat to mining safety. In view of the plane strain problems, through the three dimensional discrete model established, comparison and analysis was carried out between the equivalent calculation of plane strain in 3D model and a 2D discrete model. The results have shown that the research model developed to simulate the propagation of seismic wave in 3D is feasible and applicable. The study of the effect of radiation pattern on seismic propagation revealed and tested the direction of P-and S-wave propagation, which presents high consistency to double couple model of the fault slip. On this basis, the comparison with the design scaling law formulas proposed by Kaiser and associates finds that the existing design scaling law does not totally satisfy the demand of practical engineering. Numerical calculation and analysis with the three dimensional discrete model can further optimize the support parameters, provide better service for system design of mining support, and ensure the safety and high efficiency in mining.

  • 7.
    Chen, Xu-Guang
    et al.
    Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing.
    Wang, Yuan
    Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing.
    Zhang, Qiang-Yong
    Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan.
    Li, Shu-Cai
    Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Analogical model test and theoretical analysis on zonal disintegration based on filed monitoring in deep tunnel2013Inngår i: European Journal of Environmental and Civil Engineering, ISSN 1964-8189, E-ISSN 2116-7214, Vol. 17, nr Suppl. 1, s. 33-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Field monitoring carried out in a deep tunnel of the Dingji coal mine in China confirmed the zonal disintegration phenomenon by using the borehole TV. Based on field monitoring, an analogical model test was conducted to research the fracture shape and forming conditions of the rock mass in the Dingji mine. To perform the model test, an analogical material and optical sensor were developed independently. Through the test, the occurrence of zonal disintegration was confirmed and the forming process was monitored. The fracture pattern of zonal disintegration was determined, and the radii of the fractured zones were found to fulfil the relationship of geometric progression. The displacement laws of surrounding rocks during zonal disintegration were obtained and found to be non-monotonic. The test results are in agreement with the field-monitoring results. Through a theory analysis based on fracture mechanics, the mechanism of zonal disintegration was revealed. The fracture zones occur as circles concentric to the cavern periphery, which is the “false face”. Each fracture zone ruptures at the elastic–plastic boundary of surrounding rocks and then coalesces into a circle. The geometric progression ratio was determined; it is related to the mechanical parameters and ground stress of the surrounding rocks and calculated as follows: And the mechanism of the non-monotonic displacement law is revealed; the continuous formation of the “false face” causes the geostress redistribution and crack opening.

  • 8.
    Edelbro, Catrin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Influence of blast design on rock slope stability2002Inngår i: Proceedings of the ISRM International Symposium on Rock Engineering for Mountainous Regions, EUROCK, 2002Konferansepaper (Fagfellevurdert)
  • 9.
    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 masses2007Inngår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 22, nr 1, s. 57-68Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Eitzenberger, Andreas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Zhang, Ping
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical simulation of train-induced vibrations in rock masses2012Inngår i: Harmonising rock engineering and the environment: proceedings of the 12th ISRM International Congress on Rock Mechanics, Beijing, October 18 - 21, 2011 / [ed] Qihu Qian; Yingxin Zhou, Leiden: CRC Press/Balkema , 2012, s. 1189-1194Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The vibrations generated by a moving train in a tunnel will radiate into the surrounding ground which, in densely populated areas, will reach nearby buildings and its residents. Analyses are commonly made where the aim is to estimate the ground-borne noise and vibrations levels that may occur in nearby buildings. A common assumption is to treat the rock mass as an isotropic, homogeneous, and linear elastic material. Thus, the influence of discontinuities on the propagation of waves is not considered in the analyses. Within this study, numerical simulations were performed to study the propagation of low-frequency waves through a rock mass near a tunnel. A single period sinusoidal wave was applied as dynamic source on the floor of the tunnel. Observation points were located on the ground surface and around the tunnel. The influence on wave propagation from overburden, position of a discontinuity in relation to the tunnel, and normal and shear stiffness of the discontinuity, was studied by using the Universal Distinct Element Code (UDEC). The results show that increasing overburden reduces the vibration levels on the ground surface. Furthermore, the influence of the normal and shear stiffness of discontinuities depends on where the horizontal discontinuity is positioned in relation to the tunnel. If the horizontal discontinuity is positioned above the dynamic source (e.g. above tunnel or in the tunnel wall) the vibration levels on the ground surface will be reduced but if the horizontal discontinuity is located below the dynamic source (e.g. below the tunnel) the vibration levels on the ground surface will be enhanced. In our analyses, discontinuities only have an impact on the wave propagation if the normal and shear stiffness of is ≤10 GPa/m

  • 11.
    Elhami, Ehsan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    2D modeling of the Kristineberg mine stope2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mining operations at the Kristineberg Mine approaches depths of more than 1300 m. Severe ground conditions are consequently expected due to the combination of weak rock formations and relatively high in-situ stresses. The required support techniques, however, are not unique and depend on the ground deformation characteristics. On the other hand, the complex geology of the mining zone induces different types and magnitudes of failures. As a result, to improve the support performance, the possible ground conditions which may arise from varieties of geological parameters at the mine need to be characterized. Among different geological parameters at the mine, the location of the rock formations is seen to be an important factor, influencing the deformation behavior of the rock mass. The aim of this study is to increase the understanding of how the rock mass behavior changes due to the location of the rock formations. The study is performed through numerical modeling of an unsupported stope using FLAC2D; the required input data are determined based on the field observations and the corresponding literatures. Then, the modeled deformation behavior of the stope is studied through “Parameter Analysis”. The results, which show the sensitivity of the ground deformation to the location of the surrounding rock formations, can be used in future support design analysis.

  • 12.
    Gustavsson, Håkan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Forsling, Willis
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Forssberg, Eric
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Norrländsk vattenkraft och gruvnäring: två svenska välståndsbyggare2009Inngår i: Thule: Kungl. Skytteanska samfundets årsbok 2009, Umeå: Kungl. Skytteanska samfundet , 2009, s. 331-345Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 13.
    Hidalgo, Kelvis Perez
    et al.
    Boliden Mines Technology.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    3D Numerical Modelling of a Wedge in a Drift at the Kiirunavaara Mine2015Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 20, nr 22, s. 12309-12328, artikkel-id Paper 2015-0999Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    historic case is a field study of the mechanics of grouted rockbolts conducted in the Kiirunavaara mine between 1980 and 1983. In the drift the movement of the rock mass was recorded near the wedge, but the detailed behaviour of the wedge was not studied in the historic case. In the present work, the behaviour of the wedge is studied using field deformation measurement data and numerical analysis. The study was aimed at improving the understanding of wedge instability and associated deformations. The study shows that the behaviour of the wedge can successfully be described through evaluation of data obtained from field deformation measurement and numerical analysis. It was found that slip (shear strength reached) developed along the pre-existing joints defining the wedge. Shear deformations were thus non-elastic, but very small, and the wedge remained stable (no fallout).

  • 14.
    Hidalgo, Kelvis Pérez
    et al.
    Boliden Mineral AB.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Deformation analysis in connection with bending and shear failure of a monitored stope in the Kristineberg mine in Sweden2014Inngår i: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 5, nr 3, s. 181-201, artikkel-id 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the evaluation and interpretation of monitored deformations and field observations of a 50-m long stope at the mining depth Z1200 in the Kristineberg mine. The monitoring was conducted by Boliden Mineral AB in 2010 as a part of a research project focused on the rock support-rock mass interaction. Borehole extensometers, total stations and tape extensometers were used to monitor the stope. The objective of the presented work was to assess the deformation modes of the stope, i.e., bending and shearing. The evaluation of the data showed that the field deformation data can be used to identify bending in the HW and shear failure in the FW of the stope. The paper also shows that the deformations in the roof of the stope are influenced by the bending and shear failure. Typical deformation values related to the bending and shear failure are also estimated.

  • 15.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Basarir, Hakan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Wettainen, Thomas
    Luossavaara-Kiirunavaara AB. SE-98381, Malmberget.
    The probabilistic estimation of rock masses properties in Malmberget mine, Sweden2013Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 18, nr B, s. 269-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Numerical modeling techniques have been applied in many mining and civil engineering projects. Traditionally, deterministic methods have been used frequently for the estimation of design or input parameters for numerical modeling. Whereas, it is known that the effect of variability and uncertainty sourced from the complex and variable nature of rock cannot be considered by deterministic approaches using single or mean value. In this paper, the authors tried to apply a probabilistic approach to consider the uncertainties and variability in rock properties. This is to make more a realistic assessment of design parameters of rock masses around an instrumented test drift in Malmberget Mine within the content of the “Rock mass - Rock support interaction project” conducted at the Division of Mining and Geotechnical Engineering, Lulea University of Technology. To calculate the design parameters GSI of rock mass, UCS and mi constant of the intact rock are considered as random variables. For each of these random variables ranges were specified depending on the laboratory and field information. Using Monte Carlo simulation method a possible range of each of necessary strength and deformability properties were obtained and presented. The assessed values can be used as preliminary input parameters and considered as basis for further numerical modeling calibration studies.

  • 16.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Comparison of different probabilistic methods for analyzing stability of underground rock excavations2016Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 21, nr 21, s. 6555-6585Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stability analyses of underground rock excavations are often performed using traditional deterministic methods. In deterministic methods the mean or characteristics values of the input parameters are used for the analyses. These method neglect the inherent variability of the rock mass properties in the analyses and the results could be misleading. Therefore, for a realistic stability analyses probabilistic methods, which consider the inherent variability of the rock mass properties, are considered appropriate. A number of probabilistic methods, each based on different theories and assumptions have been developed for the analysis of geotechnical problems. Geotechnical engineers must therefore choose appropriate probabilistic method to achieve a specific objective while taking into account simplicity, accuracy and time efficiency. In this study finite difference method was combined with five different probabilistic methods to analyze the stability of an underground rock excavation. The probabilistic methods considered were the Point Estimate Method (PEM), the Response Surface Method (RSM), the Artificial Neural Network (ANN), the Monte Carlos Simulation (MCS), and the Strength Classification Method (SCM). The results and the relative merits of the methods were compared. Also the general advantages of the probabilistic method over the deterministic method were discussed. Though the methods presented in this study are not exhaustive, the results of this study will assist in the choice of appropriate probabilistic methods for the analysis of underground rock excavations. 

  • 17.
    Idris, Musa Adebayo
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Saiang, David
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Consideration of the rock mass property variability in numerical modelling of open stope stability2012Inngår i: Föredrag vid Bergmekanikdag i Stockholm, 12 mars 2012, Stockholm: Stiftelsen bergteknisk forskning - Befo , 2012, s. 111-123Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper presents a probabilistic approach for modelling complex rock masses wherethe intrinsic properties are highly variable. For this study a complex orebody in aCanadian mine is used. The mechanical properties of the host rock and the ore in thismine are found to be intrinsically variable with high contrast between their mechanicalproperties. It is apparent that the use of traditional deterministic methods to study thebehaviour of the open stopes is not appropriate for this mine. Hence, in this study aprobabilistic approach is adopted which allows the propagation of the variability of theinput parameters in the numerical modelling. Three different approaches were used toanalyze the stability of the open stopes based on the distribution of the different materialproperties of the rock mass. The results of the analysis using the three methods werecompared and the limitations and the potentials of each of the methods were discussed.The study provides insight into the significance of the rock mass property variability inthe numerical modelling of open stope stability and different ways that it could beincorporated into the modelling.

  • 18.
    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.
    Numerical analyses of the effects of rock Mass property variability on open stope stability2011Inngår i: 45th US Rock Mechanics /Geomechanics Symposium, San Francisco, CA, USA: ARMA, American Rock Mechanics Association , 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The rock mass is intrinsically variable in its physical and mechanical properties which makes it complex. This complexity is evident from the spatial random distribution of the properties from any site characterization program. The precise values for these properties are never known in most cases hence most geotechnical mine designs are based on fixed or discrete values of rock mass properties for stability analysis. This traditional deterministic approach neither reflects the inherent variability nor the uncertainty in the rock mass properties. Therefore, it is desirable to utilize a probabilistic approach which provides a range of possible results based on the variability in the rock mass properties. Understanding the effect of this random distribution and variability of the properties on stope stability is essential for more realistic mine design. In this study, a series of numerical analyses using the explicit finite difference element code FLAC, have been conducted to study the effect of the random distribution and variability of rock mass properties on the stope stability. The rock mass in the FLAC model is represented by different material properties randomly distributed to each zone. In order to compare the results, fixed average values of the material properties were also used for the FLAC model in another simulation. The results clearly indicate that rock mass property variability does affect the stope stability and that a deterministic approach to stope stability analysis could lead to conservative results.

  • 19.
    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.
    Probabilistic analysis of open stope stability using numerical modelling2011Inngår i: International Journal of Mining and Mineral Engineering, ISSN 1754-890X, E-ISSN 1754-8918, Vol. 3, nr 3, s. 194-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A probabilistic approach is presented for the analysis of open stopestability. The approach considers the inherent variability and uncertainty whichare typical of rock mass properties. In this study, a series of numerical analyseswere performed using FLAC to study the stability of open stopes while takinginto account the variability in the rock mass properties. The rock mass wasdivided into six strength classes: three classes for the host rock and threeclasses for the massive sulphide ore. Each class was randomly distributed to theelements in the FLAC model. The host rock-to-massive sulphide ore ratio isenvisaged to have a strong influence on the stope. To verify this, three casesof different ore percentages were considered and the results compared.The results, which were presented as Probability Density Functions (PDFs),indicate that the zones of low stiffness show high range of displacements andthat the increase in the percentage of the ore significantly affects the stability ofthe stopes.

  • 20.
    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 Network2015Inngår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 49, s. 307-319Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 21.
    Jing, L.
    et al.
    Royal Institute of Technology.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stephansson, Ove
    Royal Institute of Technology.
    A 3-D constitutive model for rock joints with anisotropic friction and stress dependency in shear stiffness1994Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 31, nr 2, s. 173-178Artikkel i tidsskrift (Fagfellevurdert)
  • 22. Jing, Lanru
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stephansson, Ove
    An experimental study on the anisotropy and stress-dependency of the strength and deformability of rock joints1992Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, nr 6, s. 535-542Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The anisotropy and stress-dependency of the strength and deformability of rock joints were investigated experimentally through shear tests of concrete replicas of natural rock joints. 50 concrete replicas of two natural granite joints were sheared on a servo-controlled hydraulic test frame under different magnitudes of normal stress and in different shear directions. Significant anisotropy in both the friction angle and shear stiffness of concrete replicas of joints were observed and both of them change with the variation of normal stress. The rates of dilatancy and contraction of joint samples appear to be different during cyclic shear tests, depending very much on the initial conditions of sample surfaces. Empirical relations were then postulated to describe these newly found properties of joint samples and used in developing new constitutive models for rock joints

  • 23.
    Jing, Lanru
    et al.
    Luleå tekniska universitet.
    Stephansson, Ove
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Study of rock joints under cyclic loading conditions1993Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 26, nr 3, s. 215-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A conceptual model for the behaviour of rock joints during cyclic shear and under constant normal stresses was proposed according to results from shear tests with 50 concrete replicas of rock joints. The shear strength and deformability of joint samples were found to be both anisotropic and stress dependent. Based on these experimental results, a two-dimensional constitutive model was developed for rock joints undergoing monotonic or cyclic loading sequences. The joint model was formulated in the framework of non-associated plasticity, coupled with empirical relations representing the surface roughness degradation, appearance of peak and residual shear stresses, different rates of dilatancy and contraction, variable normal stiffness with normal deformation, and dependence of shear strength and deformability on the normal stress. The second law of thermodynamics was represented by an inequality and used to restrict the values of some of the material parameters in the joint model. The new joint model was implemented into a two-dimensional Distinct Element Method Code, UDEC, and its predictions agreed well with some well-known test results.

  • 24.
    Johansson, Ola
    et al.
    Luleå tekniska universitet.
    Karlsson, Lars
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Utveckling av kolv till högfrekvent bergborrmaskin1984Rapport (Annet vitenskapelig)
  • 25.
    Johansson, Ola
    et al.
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Karlsson, Lars
    Luleå tekniska universitet.
    Utveckling av hydraulisk provbänk till bergborrmaskiner1984Bok (Annet vitenskapelig)
  • 26.
    Jones, Tristan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi. Luossavaara-Kiirunavaara AB, Malmberget, Sweden.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Wettainen, Thomas
    Luossavaara-Kiirunavaara AB, Malmberget, Sweden.
    Mining-Induced Deformation in the Malmberget Mine2019Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, nr 6, s. 1903-1916Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Norra Alliansen orebody of the Malmberget sublevel caving mine consists of iron ore interspersed with biotite schist and granitic inclusions. The schist is squeezed between the ore and the host rock and in direct contact with the ore along the majority of the length of the footwall. The schist exhibits high deformation when exposed to stress. SMART cable bolt roof deformation measurements are re-analyzed to draw conclusions regarding the patterns of deformation in the mine. Each bolt’s head is placed at the origin of a spherical coordinate system and the radius and inclination angle between the bolt and every production blast occurring during the bolt’s recorded lifetime are calculated. The deformation experienced by each instrument is investigated by comparing the long-term recorded movements with the developed geometric variables. Patterns of deformation magnitude and rate are found with respect to production-blast distance and inclination angle, instrument location, rock quality designation, and likely mining-induced stresses. Results show that deformation magnitude tends to be higher when driven by production blasting occurring on the production level above the instrumentation when accounting for the effects of distance, but average deformation magnitude for very-near production blasts tends to be higher than that for production blasts occurring directly above the instrument. Correlations also exist between the measured RQD, estimated rockmass parameters, and the measured deformation. Empirical evidence allows the identification of six scenarios which account for 91% of the recorded high-deformation-rate events. These scenarios help determine which production activities are most likely to cause high deformation rates.

  • 27. Li, C.
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Characteristics of acoustic emissions during shearing of rock joints1990Inngår i: Rock joints: proceedings of the International Symposium on Rock Joints, Loen, Norway, 4 - 6 June 1990 / [ed] Nick Barton, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1990, s. 251-258Konferansepaper (Fagfellevurdert)
  • 28.
    Li, Chunlin
    et al.
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A model for simulation of the failure of brittle rocks1993Inngår i: Safety and environmental issues in rock engineering / EUROCK '93, Lisboa, Portugal / [ed] L. Ribeiro e Sousa, Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1993, s. 143-150Konferansepaper (Fagfellevurdert)
  • 29. Li, Chunlin
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Assessment of damage in rock using the Kaiser effect of acoustic emission1993Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 30, nr 7, s. 943-946Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of our study is to explore the possibility of using the Kaiser effect method to assess damage in rock induced by blasting. Cores were drilled from a hard rock tunnel. The specimens prepared from the cores were uniaxially compressed in the laboratory and the AE from the specimens was recorded. The AE onset stress was taken as a measure of the damage in the rock induced by blasting. The results showed that the AE onset stress decreased with the distance from the tunnel floor. The extent of disturbance due to blasting could be estimated using the curve of the AE onset stress.

  • 30.
    Li, Chunlin
    et al.
    Luleå University of Technology.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Deformation of brittle rocks under compression - with particular reference to microcracks1993Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 15, nr 3, s. 223-239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A constitutive model for brittle rocks has been developed based on the analysis of microcracks. The macroscopic deformation of a rock is decomposed into three components: response of the rock matrix, closure of open cracks and deformation due to the fracture of microcracks. The main contribution of this approach is the prediction of macroscopic deformation induced by microcracking. The basic model units are sliding cracks. Wing cracks are initiated at tips of sliding cracks and propagated in the major loading direction. The relationships between the compressive stress, the length of the growing crack and deformation due to the fracture of cracks are established. A deformation solution to an elliptic crack is employed to describe the closure effect of an open crack under compression. The total deformation caused by the closure and fracture of cracks is obtained by the sum of the components of individual cracks. In this model, the nonlinear behavior of deformation results either from the closure of open cracks at low stress levels, or from the fracture of microcracks at high stress levels. Hysteresis is captured under cyclic loading. Comparisons of the model simulations with experimental data are presented and show good agreement in the prefailure stage.

  • 31.
    Li, Chunlin
    et al.
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effects of couplants on acoustic transmission1993Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 26, nr 1, s. 63-69Artikkel i tidsskrift (Fagfellevurdert)
  • 32. Li, Chunlin
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Experimental verification of the Kaiser effect in rocks1993Inngår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 26, nr 4, s. 333-351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Kaiser effect is a measure of damage developed in rock. It was investigated using 61 core specimens of eight types of rocks under uniaxial cyclic loading. The effects of the delay time between subsequent loading cycles and the holding time on the Kaiser effect were examined in granite specimens. The characteristics of AE occurring during unloading and holding were also studied. The experimental results showed that most of the rocks, with the exception of some iron ores, showed an obvious Kaiser effect before the load was very near the level of the strength. The delay and holding times did not strongly influence the Kaiser effect. Breakdown of the Kaiser effect was expressed by the felicity ratio that may be taken as a measure of the quality of rock. The onset of the continuously increasing AE in the first loading cycle can be taken as a measure of the damage in rock. The mechanism of the Kaiser effect was studied with the aid of a micromechanical model. An expression for the damage surface in the stress space was derived from the model. The theoretical expression was compared with the results of the Kaiser effect tests, which showed a satisfactory consistence.

  • 33. Li, Chunlin
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Micromechanical study of rock deformation behaviour1995Inngår i: Proceedings: 8. International Congress on Rock Mechanics : Tokyo, Japan, 1995 = Comptes-rendus / International Society for Rock Mechanics / [ed] T. Fujii, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1995, s. 237-240Konferansepaper (Fagfellevurdert)
  • 34. Li, Chunlin
    et al.
    Prikryl, Richard
    Institute of Mineralogy, Geochemistry and Mineral Resources, Charles University, Prague.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Stress-strain behaviour of rock material related to fracture under compression1998Inngår i: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 49, nr 3/4, s. 293-302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fracture is the main reason for the non-linear behaviour of hard rocks. The fracture mechanics of rock is studied in this article by analysis of the fracture process under compression. A constitutive model that describes the relationship between the macro deformation of rock and the micro fracture within rock is developed. The propagation of microcracks, the non-linearity of deformation, the loading-and-unloading hysteresis and the variation of the apparent Young's modulus and Poisson's ratio are studied using the developed model. The model simulations demonstrate that: (1) the fracture toughness, initial crack length, crack density, and Young's modulus are four crucially important parameters that affect the deformation behaviour of rock; (2) the elastic parameters (E and v) of the rock matrix should be measured in triaxial tests. If they are measured in uniaxial tests, the upper straight unloading portion of the stress-strain curve is suggested to be used for the purpose, unless the closure effect of open cracks will be included in the estimations. In addition (3), the slope of the reloading stress-strain curve is a measure of the damage in material.

  • 35. Li, Chunlin
    et al.
    Stephansson, Ove
    Luleå tekniska universitet.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Determination of stress and damage levels of rocks using acoustic emission and the kaiser effect1988Rapport (Annet vitenskapelig)
  • 36.
    Mainali, Ganesh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dineva, Savka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Experimental study on debonding of shotcrete with acoustic emission during freezing and thawing cycle2015Inngår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 111, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    tudying the deterioration of shotcrete due to freezing and thawing is important for improvement of the understanding of the failure mechanisms/debonding of shotcrete in cold regions. Water leakage in a tunnel leads to ice growth during freezing temperature and ultimately creates favorable environment for fallouts of shotcrete and rock. Repeated freezing and thawing of shotcrete lead to development of new micro cracks and propagation of pre-existing micro cracks. In this study, test panels of granite with dimension 800 x 800 x 80 mm covered with 50-mm thick shotcrete were subjected to freezing and thawing action in a controlled environment. The initiation and the development of freeze-induced micro cracks in shotcrete-rock interface were studied by continuously monitoring acoustic emissions (AE) and temperature. The clustering of the AE events during freezing and thawing indicates that micro cracks appeared in the shotcrete-rock interface and caused adhesion failure. The larger number of AE events in the panels, with access to water during freezing, confirmed that water contributes to material deterioration and also reduces the adhesive strength. The test results showed that most of the acoustic emission occurred during the freezing cycle and the number of acoustic emission events did not increase with the successive increase of the number of freezing and thawing cycles.

  • 37.
    Mainali, Ganesh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dineva, Savka
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Laboratory investigation of rock-shotcrete debodningdue to ice growth using acoustic emission2016Inngår i: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E . Nordlund, T.H. Jones and A. Eitzenberger (eds), 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Road and railway tunnels in cold regions are often affected by problems related to water leakage and freezing temperatures. Water leakage in a tunnel leads to ice growth when the temperature goes below freezing and creates favourable environment for fallouts of shotcrete and rock. This paper presents results and observations from laboratory freezing – thawing experiments on rock blocks covered with shotcrete and focuses on the degradation of the shotcrete-rock interface due to ice growth.. The initiation and the development of freeze-induced micro cracks in shotcrete-rock interface were studied by continuously monitoring acoustic emissions (AE) and temperature. The clustering of the AE events during freezing and thawing indicates that micro cracks appeared in the shotcrete-rock interface and caused adhesion failure. The larger number of AE events in the panels, with access to water during freezing, confirmed that water contributes to material deterioration and also reduces the adhesive strength.

  • 38. Mainali, Ganesh
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Thunehed, Hans
    Geovista AB.
    Tailings dams monitoring in Swedish mines using self-potential and electrical resistivity methods2015Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 20, nr 13, s. 5859-5875Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailings dam failures have been occurring in recent years. Many of these failures have caused human casualties, destruction of property, and damage to environment and huge economic loss to the mining industry. The monitoring of the dam is essential to know the existing state of the dams and to ensure the safety of the dam over its life time. The present study has been conducted to test the applicability of electrical resistivity and self-potential (SP), for detecting anomalous seepage through mine tailings dams in Sweden and monitoring the physical condition of the dam. This study has demonstrated the potential of using geoelectrical methods for monitoring the conditions of the tailing dams related to seepage.

  • 39. Malmgren, Lars
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Behaviour of shotcrete supported rock wedges subjected to blast-induced vibrations2006Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, nr 4, s. 593-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The static state of stress at the brow in a sub-level caving mine is, due to stress re-distribution, almost uniaxial (major principal stress perpendicular to the cross cut). Since large amounts of explosives are detonated in each production round, the impact of stress waves on the brow can be significant. An extensive failure mapping programme in the Kiirunavaara mine showed that many of the failures close to the brow were structurally controlled. Furthermore, the area of damaged shotcrete was extensive when plain shotcrete was used. At brows supported by fibre reinforced shotcrete, damage in the roof was observed within a horizontal distance of about 3 m from the drawpoint. To study the behaviour of roof wedges supported by shotcrete and subjected to blast-induced vibrations a single-degree-of-freedom (SDOF) model was developed. The model consists of a shotcrete layer and a rock wedge. Vibration measurements showed that maximum particle velocity was approximately 1.2 m/s. The acceleration record showing the largest magnitude was used as the load in the dynamic analyses. The analyses showed that a wedge can be ejected by a dynamic load even if the static safety factor was >10. Furthermore, the non-linear response of the wedges was in most of the cases greater when the wedge was supported both by the joints and the shotcrete layer compared to the case when the wedge was only supported by shotcrete. A conclusion from the analyses is that it is difficult to predict the dynamic response from static calculations. To provide a safe working environment close to the drawpoint, the rock support must sustain the impact of stress waves from production blasting. To support rock wedges subjected to dynamic load the support must be able to consume the energy imposed on the wedges from blasting. The non-linear numerical analyses showed that reinforced shotcrete has the necessary bearing capacity to support the wedges formed in the roof of the cross cut close to the brow. This was in fair agreement with the failure mapping. The single-degree-of-freedom (SDOF) model can be used to study the response of an arbitrarily shaped rock wedge supported by shotcrete as long as the movement of the wedge can be idealised by a pure translation and the dimensions of the wedge are small compared to the length of the incident wave. Analyses showed that 2D wedges can be used to judge whether symmetric or non-symmetric 3D wedges in a uniaxial stress field (which occurs close to the brow) are stable or not when they are subjected to waves induced by blasting.

  • 40. Malmgren, Lars
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Interaction of shotcrete with rock and rock bolts: a numerical study2008Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, nr 4, s. 538-553Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The shotcrete-rock interaction is very complex and is influenced by a number of factors. The influence of the following factors was investigated by a series of numerical analyses: the surface roughness of the opening, the rock strength and Young's modulus, the discontinuities, the extent and properties of the excavated disturbed zone, the mechanical properties of the interface between shotcrete and rock, and the thickness of the shotcrete lining and the rock bolts. The study was carried out as a sensitivity analysis. The results showed that the rock strength and the surface roughness had significant impact on the number of failures at the rock-shotcrete interface and in the shotcrete lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. In all the cases investigated, a high interface strength was favourable. The results indicate that if a thick shotcrete lining is dependent on the bond strength. The benefit of using a thicker lining can be doubtful. The analyses showed that for an uneven surface the extent of the EDZ had a minor effect on the behaviour of the shotcrete lining. Furthermore, if rock bolts were installed at the apex of the protrusion instead of at the depression, the number of failures decreased both at the interface and in the lining

  • 41. Malmgren, Lars
    et al.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rolund, S.
    WSP, Malmberget.
    Adhesion strength and shrinkage of shotcrete2005Inngår i: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 20, nr 1, s. 33-48Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 42.
    Nilsson, Mikael
    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.
    Fracturing in the footwall at the Kiirunavaara mine, Sweden2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Kiirunavaara mine is a large scale sub level caving (SLC) mine located near the city of Kiruna in northern Sweden. It is owned and operated by LKAB (Luossavaara-Kiirunavaara AB). The mine produces approximately 28 million tonnes of iron ore annually. Over the last 30 years the mine has experienced a slow but progressive fracturing and movement in the footwall rock mass induced by the SLC operations. The footwall contact which assumes a “slope-like” geometry is partially supported by the caved material from the hangingwall. However, since the late 1980s damage has been observed on the footwall crest as well as within the footwall. Progressive rock mass movement in the footwall is indicated by surface subsidence and visual observations underground. The extent of the damage has traditionally been estimated using empirical relations. Most of the current long term underground infrastructure within the footwall is located at a considerable distance from the ore contact. However, for new developments on deeper levels it is imperative to predict the future extent of the damage volume. Approximating the position of the damage boundary in the footwall at the current state of mining would assist in predicting the extent and characteristics of the damage volume as the mine deepens. LKAB and LTU (Lulea University of Technology) have therefore initiated a joint research project to study the long term stability of the footwall at the Kiirunavaara mine. This paper constitutes part of the work in this research.The paper describes a damage mapping campaign and subsequent analysis of the Kiirunavaara mine footwall to approximate the outer boundary of the damage. The footwall was systematically mapped on 6 levels between 320 and 800 m. The mapping results were then used to interpolate damage lines on the respective levels. The damage lines were used to construct a continuous damage surface between the studied levels. Existing records of damage mapping, monitoring and predictions were reviewed and compared to the results from the current campaign. The new results show that, the outer damage surface appears to remain stationary on the upper levels while new damage was observed on the deeper levels. At levels above 740 m the damage is judged to be mainly controlled by movements along natural discontinuities. At levels below 740 m the majority of the damage seems to be stress induced.

  • 43.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effect of thrust on the performance of percussive rock drills1989Inngår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, ISSN 0148-9062, E-ISSN 1879-2073, Vol. 26, nr 1, s. 51-59Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance of two different percussive rock drills has been studied theoretically by simulating the drilling process. The two drills studied correspond to an idealized drill and a more complex, prototype drill. The efficiency, the maximum stress (maximum tensile stress) and the minimum stress (maximum compressive stress) have been determined during the simulations. Also, the stability of the drill string with respect to buckling has been estimated as a function of a constant applied thrust. Two cases of applied thrust were simulated. They correspond to a constant applied thrust and an applied thrust with time dependent harmonic variations. The results show that for low frequency variations in thrust, the performance of the rock drill is almost the same as for a constant applied thrust. It was assumed in the remainder of this study that the applied thrust can be treated as a constant force. The results obtained for a constant applied thrust are summarized.

  • 44.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Experimental study of impact-loaded conical friction joints1983Rapport (Annet vitenskapelig)
  • 45.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Experimental study of impact-loaded cylindrical friction joints1983Rapport (Annet vitenskapelig)
  • 46.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Impact loaded conical friction joints1983Rapport (Annet vitenskapelig)
  • 47.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Impact loaded cylindrical friction joint1983Rapport (Annet vitenskapelig)
  • 48.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Impact mechanics of friction joints and percussive drills1986Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Impact-loaded conical and cylindrical friction joints are studied theoretically and experimentally. The system considered consists of a long, straight, cylindrical and linearly elastic rod which is impacted axially at one end, and which has a body attached by means of a friction joint at the opposite end. The conditions are such that the wave propagation is 1-D in the rod and can be neglected in the attached body. Slip and energy dissipation due to an impact load are determined. The theoretical results of the impact-loaded conical friction joints exhibit phenomena which sometimes have spectacular appearance. The agreement between theoretical and experimental results is fair. The influence of blow frequency and thrust on the performance of a percussive rock drill is studied theoretically. The drill considered consists of hammer, adapter, rod and bit. Two different rock drills are studied. The first is a simple drill with constant characteristic impedance throughout the drill. The second is a prototype of a high frequency percussive rock drill. The efficiency and the maximum (maximum tensile) and minimum (maximum compressive) stresses are determined. For the simple drill the average efficiency in the range from soft to hard rock is only weakly dependent on the blow frequency up to relatively high blow frequencies but strongly dependent for extremely high blow frequencies. It is also found that the maximum and minimum stresses in the drill in the range from soft to hard rock are only weakly dependent on the blow frequency up to high frequencies but strongly dependent for extremely high frequencies. The maximum stress increases and the minimum stress decreases with thrust.

  • 49.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Numerical study of tunnels at shallow depth in an urban area1999Inngår i: FLAC and numerical modeling in geomechanics: proceedings of the International FLAC Symposium on Numerical Modeling in Geomechanicsm, Minneapolis, Minnesota, USA, 1 - 3 September 1999 / [ed] Christine Detournay, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1999, s. 263-270Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two parallel traffic tunnels will be excavated under a building which is extremely sensitive to ground subsidence. The building is founded on pillars that transfer the weight of the building to the rock surface above one of the tunnels. A numerical investigation has been carried out to study if the subsidence of the pillars and the displacements of the tunnel boundaries will be acceptable or not. The problem was simplified assuming two-dimensional conditions and linear elastic conditions and the sensitivity to changes in the input parameters were studied. The analyses showed that the subsidence of the pillars increased by 100% (< 0.6 mm) due to the excavation of the tunnels. Furthermore, the pillar loads resulted in a tunnel roof deformation which was 400 % (1 mm) greater than for a case without any load at the ground surface.

  • 50.
    Nordlund, Erling
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Slip and energy dissipation in cylindrical friction joints loaded by impact-induced waves1987Inngår i: International Journal of Impact Engineering, ISSN 0734-743X, E-ISSN 1879-3509, Vol. 6, nr 1, s. 35-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cylindrical friction (CYLF) joints subjected to impact-induced wave (IIW) loading are studied theoretically and experimentally. The system considered consists of a long, straight, cylindrical and linearly elastic rod which is impacted axially at one end by a cylindrical and linearly elastic hammer. A body is attached at the other end by means of a CYLF joint. The conditions are such that the wave propagation is 1-D in the hammer and the rod and can be neglected in the attached body which is therefore treated as rigid. The agreement between numerical and analytical solutions is good. There is also fair agreement between theoretical and experimental results.

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