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  • 1.
    Botelho, Anneliese H.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Velocity amplification of obliquely incident s-wave through fractures near free-surface2019In: Rock Mechanics for Natural Resources and Infrastructure Development - Full Papers: Proceedings of the 14th International Congress on Rock Mechanics and Rock Engineering (ISRM 2019), September 13-18, 2019, Foz do Iguassu, Brazil / [ed] Sergio A.B. da Fontoura; Ricardo Jose Rocca; José Pavón Mendoza, Taylor & Francis, 2019, p. 1487-1494Conference paper (Refereed)
    Abstract [en]

    The rockfall risk due to mining-induced seismicity reduces by installing appropriate rock support to absorb the kinetic energy from a seismic event, which is calculated by assuming the mass of ejected rock and its ejection velocity. Estimation of ejection velocity is normally based on scaling laws that do not consider the effect of the excavation free-surface and existing fractures near the excavation free-surface. Field monitoring studies have shown that the peak particle velocity on the free-surface can be much larger than the velocity in deep solid rock. The interaction between the fractures and the free-surface under incident S-wave is investigated by using a two-dimensional UDEC model with fractured zone characterized as one, two, three and four sets of parallel fractures with varied intersecting angles. The results show that wave amplification factor varies according to the incident wave angle, the number of fracture sets and fracture spacing.

  • 2.
    Botelho, Anneliese H.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. CNPq - Brazil.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effects of parallel fractures near a free surface on velocity amplification of S-wave2017In: Proceedings of the Ninth International Symposium on Rockbursts and Seismicity in Mines / [ed] Javier Vallejos, Santiago do Chile: University of Chile , 2017, , p. 337Conference paper (Refereed)
    Abstract [en]

    When rock support is designed in a seismically active underground mine, it is important tochoose the right ejection velocity and calculate corresponding kinetic energy. Field monitoringand back-analyses have shown that ejection velocity of the order of 10 m/s and higher can resultfrom seismic events of moderate magnitude. Such velocities are much higher than those predictedusing peak particle velocity (PPV) obtained from scaling laws. Many researches have reportedthe amplification of particle velocity near excavation surface. Velocity amplification of P-wavetravelling through fractured rock near a free surface was recently studied. The amplification ofseismic waves on the skin of excavation is of interest in case of large seismic events. Seismic eventswith large magnitude are often associated with slip along weaknesses or shear fracturing of intactrock, which according to observations radiate much stronger S-wave as compared to P-wave.In this paper, velocity amplification of S-wave was investigated by modelling the dynamicinteraction between fractured rock and a free surface using a 2D discontinuum-based numericalprogram, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone wasused to represent the fractured rock in this investigation. It is found that the shear stress ratio,wave frequency, fracture stifness, fracture spacing and thickness of fractured zone afect thevelocity amplification, in which the shear stress ratio is the most crucial factor influencing wavetransmission. The results have proved that the interaction of the seismic wave and multiplefractures near the free surface strongly influences the ground motion.

  • 3.
    Chen, Guanghui
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Li, Xibing
    School of Resource and Safety Engineering, Central South University, Changsha, Hunan.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    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 burst2017In: Journal of Mining and Safety Engineering, ISSN 1673-3363, Vol. 34, no 4, p. 715-722Article in journal (Refereed)
    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.

  • 4.
    Eitzenberger, Andreas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical simulation of train-induced vibrations in rock masses2012In: 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, p. 1189-1194Conference paper (Refereed)
    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.

  • 5.
    Ma, Xu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Investigation of Unstable Failure Potential of a Shear Slip Using DEM at an Underground Mine2021In: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 11, no 3, p. 59-83Article in journal (Refereed)
    Abstract [en]

    During the winter season, ice causes major problems in many Swedish railway tunnels. Ice, rock and shotcrete in the roof and on the walls may come loose and fall down, installations and cables can break due to ice loads and the tracks can become covered with ice. To maintain safety and prevent traffic disturbances, many tunnels require frequent maintenance. The removal of ice, loose rock and shotcrete is expensive and potentially risky work for the maintenance workers. To reduce maintenance costs, it is important to improve our knowledge of frost penetration inside tunnels and investigate the effect of ice pressure and frost shattering on load-bearing constructions. The aim of this investigation was to gather information about the problems caused by water leakage and its effect on the degradation of a rock tunnel when subjected to freezing temperatures. There are many factors that determine whether frost or ice formations will appear in tunnels. To collect information on ice formation problems, field observations were undertaken in five of Sweden’s railway tunnels between autumn 2004 and summer 2005. For one of the tunnels, follow-up observations also took place in March during the years 2005, 2006 and 2007.

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  • 6.
    Ma, Xu
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing, China.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Unstable Shear Slip Failure and Seismic Potential Investigation Using DEM in Underground Mining2023In: Mining, Metallurgy and Exploration, ISSN 2524-3462, Vol. 40, no 1, p. 405-420Article in journal (Refereed)
    Abstract [en]

    Perturbations arising from mining operations significantly affect the stability of rock masses, and the influences aggerates with the rapid increase of mining-operation depths during recent years. The subsurface structures with major discontinuities subject to seismic hazards resulted from the shear-slip behaviors of rock masses. In order to identify the shear-slip regime of discontinuities and calculate seismic moment and seismic energy involved with shear-slip behaviors, we use discrete element modeling to study the shear slip failure along discontinuities in an underground mine. The recorded characteristic and properties of sub-contacts in DEM provide a basis for computing and visualizing the temporal and spatial distribution of seismic moment and seismic energy with mining operations. We computed the seismic energy and seismic moment using the numerical modeling method and the analytic method. We compared the result of summing seismic energy and seismic moment from the subcontacts of numerical models and the result of the analytic method. We confirmed that this tool can be used in comparative analyses. We also found that seismic moment and seismic energy, associated with shear stress drop and shear displacement increase, accumulate in the vicinity of major discontinuities. Mining operations at a greater depth cause greater changes of seismic moment and seismic energy, leading to a higher risk of inducing seismic hazards. Quantifying seismic potential using discrete element modeling can greatly facilitate the investigation of instability of geological discontinuities and thereby can help estimate the potential of seismic hazards.

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    fulltext
  • 7.
    Nordlund, Erling
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzadegan, Shahin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Westblom, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Marklund, P-I
    Boliden Mineral AB.
    Sandström, D.
    Boliden Mineral AB.
    Malmgren, Lars
    Samverkan mellan bergförstärkningssystem och bergmassa2011In: Bergmekanikdag 2011: Föredrag, Stiftelsen bergteknisk forskning - Befo , 2011, p. 19-28Conference paper (Other academic)
  • 8.
    Nordlund, Erling
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Basarir, Hakan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzaegan, S.
    Luleå University of Technology.
    Westblom, Magnus
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    LKAB.
    Marklund, P-I
    Boliden Mineral AB.
    Nordqvist, A.
    LKAB.
    Sandström, D.
    Boliden Mineral AB.
    Rock support system in interaction with the rock2011Conference paper (Other academic)
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  • 9.
    Nordlund, Erling
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, David
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mainali, Ganesh
    Impact of fire on the stability of hard rock tunnels in Sweden2015Report (Refereed)
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  • 10.
    Nordström, Emilia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Andersson, Ulf B.
    Warema, Senzia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Qualitative and quantitative analysis of damages caused by seismic events in Kiirunavaara mine, SwedenManuscript (preprint) (Other academic)
  • 11.
    Nordström, Emilia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    A methodology for a rock mechanic seismic damage hazard analysis in seismically active minesManuscript (preprint) (Other academic)
  • 12.
    Sayahi, Faez
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical simulation of the response of an underground opening at different locations under fault-slip induced seismic wave2013In: The Second Nordic Rock Mechanics Symposium, Stockholm: Stiftelsen bergteknisk forskning - Befo , 2013, p. 199-205Conference paper (Refereed)
    Abstract [en]

    With increasing mining depth and thus higher stress environments, rockbursts are becoming an increasing problem world-wide. Much research has been directed toward establishing a rockburst hazard assessment method by relating seismic source intensity to the peak ground motion characteristics at an opening and further by involving some empirical indices (e.g. excavation vulnerability potential). However, the interaction between seismic waves and the excavation surfaces is not taken into account. In this paper the influence of fault-slip induced seismic waves on openings has been investigated. The effect of the location and orientation with respect to the hypocenter of the seismic event has been investigated. Openings located at the same distance from the source but at eight different orientations were numerically analyzed using the discontinuum code UDEC. The results show that the opening’s location plays a significant role for the Peak Particle Velocity (PPV) on their boundaries. It was found that the PPV is highly influenced by the P-wave and S-wave radiation patterns. The amplitude and direction of the PPV show anisotropic behavior, even when the distance from the target to the seismic source is the same. The anisotropic behavior of the PPV becomes more pronounced with increasing distance to the seismic source. The study shows that the magnitude-distance-PPV method used in support design and rockburst hazard assessment needs to be reconsidered in order to take the effect of wave radiation pattern into account.

  • 13.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Rock support subjected to dynamic loading: Field testing of ground support using simulated rockburst2011In: 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 , 2011, p. 1269-1273Conference paper (Refereed)
    Abstract [en]

    Increasing the mining depth at LKABs Kiirunavaara mine located in the northern part of Sweden is leading to higher stress magnitudes, resulting in increased seismic activity and more rockburst damage. The effectiveness of various ground support systems under dynamic loading conditions has therefore become of prime interest to LKAB for successful and safe mining at deep levels. Therefore, a series of rockburst simulations will be conducted, using explosives to generate the dynamic load, on a number of support systems. This paper covers the results from the first trial test called Zero test-1. The test included ground motion measurements with a number of accelerometers, fracture investigation, ground and support motion imaging, as well as the deformation measurements. The methodology used to simulate rockbursts is discussed and the issues met in these tests are also addressed for further improvement.

  • 14.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Development of a methodology for in-situ dynamic testing of ground support2015Conference paper (Other academic)
    Abstract [en]

    A series of seven large scale dynamic tests were conducted at LKAB Kiruna mine using explosives in the vicinity of cross-cuts to generate dynamic load on the support system. The aim was to develop an in-situ testing method for rock support, i.e., to determine the dynamic load that causes failure to the test wall and/or support system. The methodology used to design Tests 1 to 7 is discussed in this paper and the level of damage to the test wall and support system in each test is described. Comparison of results in different test designs indicated that increasing burden and number of blasthole at the same time, increases the possibilities of obtaining more planar waves and decreases the destructive effect of detonation gases.

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  • 15.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    In-situ dynamic testing of rock support at LKAB Kiirunavaara mine2016In: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E . Nordlund, T.H. Jones and A. Eitzenberger (eds), 2016Conference paper (Refereed)
    Abstract [en]

    A series of large scale dynamic tests were conducted at the LKAB Kiirunavaara mine using explosives to generate the dynamic load on the support system. This was done with the aim of developing a testing methodology for in-situ testing of ground support. Furthermore, the response of the installed rock support system to strong dynamic loading was evaluated. The results of the Tests 1, 2, 3, 4 and 5 indicated that the relation between the burden and the used amount of explosive had a vital role in either reducing or involving the effect of the detonation gases in the test results. Higher peak particle velocities were measured compared to those of similar large scale tests carried out in other countries. However, the level of induced damage in Tests 1 and 2 was limited to a fractured zone behind the support system while in Tests 4 and 5 the burden was unexpectedly destroyed. Based on the test results and preliminary numerical analysis, a modified test (Test 6) was designed at the same mine. The aim 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. 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. Evidence from the damage to the tested cross-cuts in Test 6 indicated a reduction of radial cracks that provide access for the gas expansion. The results indicated that the installed support system, designed for dynamic conditions, performed well under the loading conditions which can cause ejection

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  • 16.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Large scale dynamic testing of rock support at Kiirunavaara: Improved test design2016In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 59, p. 183-198Article in journal (Refereed)
    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.

  • 17.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Large Scale Dynamic Testing of Rock Support System at Kiirunavaara Underground Mine2016In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 49, no 7, p. 2773-2794Article in journal (Refereed)
    Abstract [en]

    A series of five large scale dynamic tests were conducted at the LKAB Kiirunavaara mine using explosives to generate the dynamic load on the support system. This was done with the aim of developing a testing methodology for in situ testing of ground support. Furthermore, the response of the installed rock support system to strong dynamic loading was evaluated. The tests included ground motion measurements, fracture investigation, ground and support motion imaging, as well as deformation measurements. The results indicated that the relation between the burden and the used amount of explosive had a vital role in either reducing or involving the effect of the detonation gases in the test results. In addition, the type of explosive which was used in the tests had a great impact on minimising the gas expansion effects. Higher peak particle velocities were measured compared to those of similar large scale tests carried out in other countries. However, the level of induced damage was limited to a fractured zone behind the support system and propagation of cracks in the shotcrete. Measured peak particle velocities were used to calculate the kinetic energy transmitted to the fractured zone of the test wall. The energy absorption by the Swellex, reinforced shotcrete and weld mesh was estimated by measuring the elongation/deflection of the support elements and relating these measurements to previously conducted laboratory tests. The comparison of maximum estimated energy absorbed by support system with the maximum estimated kinetic energy indicated that as the support system is still functional, the energy is partly reflected back to the surrounding rock. The results of the measurements in Tests 1, 2, 4 and 5 are presented in this paper and the methodology used to design the tests is discussed.

  • 18.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Nordqvist, Anders
    LKAB.
    Andersson, Ulf Bertil
    LKAB.
    Large-scale dynamic testing of ground support system at the Kiirunavaara underground mine: Test 12013Report (Other academic)
  • 19.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    LKAB Research and Development.
    Nordqvist, Anders
    LKAB.
    Andersson, Ulf Bertil
    LKAB.
    Large-scale dynamic testing of ground support system at the Kiirunavaara underground mine: Tests 4 & 52013Report (Other academic)
  • 20.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Nordqvist, Anders
    LKAB.
    Andersson, Ulf Bertil
    LKAB.
    Large-scale dynamic testing of rock support system at the Kiirunavaara underground mine: Tests 2 & 32013Report (Other academic)
  • 21.
    Shirzadegan, Shahin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Töyrä, Jimmy
    LKAB.
    Nordqvist, Anders
    Andersson, Ulf Bertil
    LKAB.
    Large-scale dynamic testing of ground support system at the Kiirunavaara underground mine: Tests 6&72013Report (Other academic)
  • 22.
    Taleghani, Pouria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Thermal spalling and fracturing around cylindrical opening in rock under biaxial loading condition: observations and analysis2013In: The Second Nordic Rock Mechanics Symposium, Stockholm: Stiftelsen bergteknisk forskning - Befo , 2013, p. 107-120Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to experimentally investigate the effect of the initial compressive stress and a circular opening boundary on thermal spalling and determine the mechanism causing thermal damage (spalling and fracturing) in rock observed in laboratory experiments. This was done by testing seven blocks of oven-dried and water-stored granite, gabbro and schist. The rock blocks had the dimensions 600 mm  500 mm  300 mm and a 75 mm borehole was drilled through the centre of each block to resemble a tunnel. The blocks were heated up approximately following a hydrocarbon fire curve. During the tests, both temperature and acoustic emissions were recorded.It is concluded that the tested rocks presented fairly different behaviours during fire due to different mineralization and thermal expansion coefficients. The granite suffered explosive spalling under confined conditions for both oven-dried and water-stored samples. The spalling was a continuous process and was repeated as long as the conditions were met. The gabbro suffered only relative small damage as small pieces flew off the fire exposed surface. Since the layers of the schist were located perpendicular to borehole axis, no obvious spalling was observed but the layers separated after testing due to expansion along the borehole axis. Compared to oven-dried samples, water-stored samples displayed more thermal spalling on granite and gabbro. The tests also showed that the initial compressive stress has facilitated spalling by means of reducing tensile stresses within the rock block and increasing the compressive stress concentration near the opening boundary.

  • 23.
    Warema, Senzia
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Nordström, Emilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yi, Changping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Analysis of the rock mass support damages for seismic damaging events in Kiirunavaara mineManuscript (preprint) (Other academic)
  • 24.
    Wu, Cheng
    et al.
    Hunan University.
    Zhang, Ping
    Analysis of numerical simulation methods for excavation failure zone of deep underground opening in hard rocks with high geostress2012In: Hydrogeology & Engineering Geology, ISSN 1000-3665, Vol. 39, no 6, p. 35-42Article in journal (Refereed)
    Abstract [en]

    With the construction of deep underground openings, the formation of excavation failure zone and its prediction have become a focus of rock mechanics in deep underground excavation both in China and abroad. Based on the analysis of mechanical properties of hard rocks during their failure process, the conventional continuum models and the cohesion weakening-friction strengthening(CWFS)model were compared. Numerical analysis of a circular test tunnel in a Mine-by Experiment at the URL in Canada was carried out by using FLAC with elastic-perfectly plastic, elastic brittle, strain softening and CWFS constitutive models respectively. The results of comparison of stress distribution, principal stress values at key points and plastic region among different models show that CWFS model can simulate the stress transfer and stress concentration to a deep area, which is the real situation when stress-induced failure occurs; the stress distribution calculated from CWFS model is much closer to that when the excavation failure zone is deleted. Compared to other models, the extent and depth of excavation failure zone calculated by CWFS are larger and they are in agreement with the field measurement. Finally, the CWFS model was used to investigate the failure zone in another case, the Kobbskaret road tunnel in Norway. The depth and extent of the excavation failure zone were predicted rather well and it again proves the rationality of using CWFS model in predicting the excavation failure zone of hard rocks in deep tunnels.

  • 25.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Lu, Wenbo
    Rock Mechanics in Hydraulic Structural Engineering, Ministry of Education.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of imperfect interface on the dynamic response of a circular lined tunnel impacted by plane P-waves2016In: Tunnelling and Underground Space Technology, ISSN 0886-7798, E-ISSN 1878-4364, Vol. 51, p. 68-74Article in journal (Refereed)
    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.

  • 26.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Warema, Senzia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzadegan, Shahin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical modeling for a simulated rockburst experiment using LS-DYNA2021In: Underground Space, ISSN 2467-9674, Vol. 6, no 2, p. 153-162Article in journal (Refereed)
    Abstract [en]

    Ground support systems are commonly used to mitigate the potential consequences of rockburst in burst prone mines. To assess the capacity of ground support systems when subjected to dynamic loading, simulated rockburst tests using blasting were conducted at the Kiruna Mine. In this study, a numerical simulation for one of the field tests was conducted using the LS-DYNA code to investigate the dynamic response of the ground support systems including shotcrete and rockbolts. The numerical results showed a similar particle vibration pattern and a crack pattern to those of the field measurements. The effects of the detonator position and the charge configuration on the dynamic response of ground support systems are also discussed. Numerical results indicated that the peak particle vibrations on the tested panel increase along the direction of detonation propagation. It is difficult to use different charge concentrations in one borehole to investigate the effect of different dynamic loads on the dynamic response of support systems. Numerical results also indicated that 2D numerical modeling for simulated rockburst experiments could overestimate the dynamic response of ground support systems.

  • 27.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dynamic analysis for a circular lined tunnel with an imperfectly bonded interface impacted by plane SH-waves2014Conference paper (Refereed)
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  • 28.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Daniel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dynamic response of a circular lined tunnel with an imperfect interface subjected to cylindrical P-waves2014In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 44, p. 165-171Article in journal (Refereed)
    Abstract [en]

    The analytic solutions for the dynamic response of a circular lined tunnel with an imperfect interface subjected to a cylindrical P-wave were presented in the paper. The wave function expansion method was used and the imperfect interface was modeled with a spring model. The interface separating the liner from the surrounding rock was considered to be homogeneous imperfect. The dynamic stress concentration factors (DSCF) of the rock and liner were evaluated and discussed. The effects of incident wave’s frequency, bonding conditions and distance between the wave source and the tunnel were examined. The results showed that the low-frequency incident wave leads to a higher DSCF than the high-frequency incident wave. The bonding conditions have a great effect on the dynamic response of the lined tunnel. When the bond is extremely weak, the resonance scattering phenomenon can be observed. When the distance between the wave source and the tunnel, depending on frequency of the incident wave, is considered as large, the cylindrical wave can be treated as a plane wave. Limiting cases were considered and good agreement with the solutions available in the literature was obtained.

  • 29.
    Yi, Changping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzadegan, Shahin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical modelling of dynamic response of underground openings under blasting based on field tests2016In: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E. Nordlund, T.H. Jones and A. Eitzenberger (eds), 2016Conference paper (Refereed)
    Abstract [en]

    In order to assess the capacity of ground support systems when subjected to dynamic loading, simulated rockburst tests by using blasting have been conducted at LKAB Kiirunavaara underground mine. In this paper, a numerical simulation for one of the field tests is conducted using LS-DYNA code to numerically investigate the effect of the different aspects of the charge design including the initiation point and the geometry on the test results. In the simulation, an explosive material model is used to model the detonation of explosive used in field tests and the Riedel-Hiermaier -Thoma (RHT) material model is used to model the dynamic response of the rock mass. The decoupling effect between the explosive and the wall of borehole is also taken into account in the model. The numerical results show a similar particle vibration pattern and a crack pattern to those of the field measurment. The effects of the position of the initiation point and the charge structure on the dynamic response of rock mass are also discussed. The results can be a reference for blast design for future field tests.

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  • 30.
    Ylmefors, Andreas
    et al.
    LKAB, Malmberget, BD, Sweden.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mozaffari, Shahram
    LKAB, Kiruna, BD, Sweden.
    Classification of Mining Induced Seismicity at the Kiirunavaara Mine2022Conference paper (Refereed)
    Abstract [en]

    The risk associated with mining induced seismicity and the related rock bursts has become one of the major threats to the safety and sustainability of mining at the Kiirunavaara mine, Sweden. The mine is owned by LKAB and is using sublevel caving mining method. The causes of mining induced seismicity at the Kiirunavaara mine are very complex, due to complex ore body geometry, mining sequences, infra-structures, geological and stress conditions, etc. These have affected our understanding on the source mechanisms of seismicity and further the mitigation of the seismic risk.

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  • 31.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    A 3DEC numerical analysis of the interaction between uneven rock surface and shotcrete lining: Validation of physical model and evaluation of influence of unevenness on the support effect of shotcrete2013Report (Other academic)
    Abstract [en]

    Although shotcrete (sprayed concrete) has been widely used as rock support in mines and in civil engineering projects, the complex interaction between shotcrete and rock has not been studied well. The main reason is that the performance of shotcrete is influenced by a number of important parameters.Experiences from previous research and past projects show that the unevenness of rock surface has a large impact on the number of failures at the interface and in the lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. Although people have done some experimental and numerical analysis, the influence of the complex unevenness of three dimensional shaped surfaces on the shotcrete – rock interaction has not been well studied.The project here focuses on the influence of the surface unevenness of a circular opening on the support effect of shotcrete. The work was done by using a 3D numerical simulation (3DEC) and was conducted in two stages. In stage 1, the numerical model was validated by comparing with physical model tests by Chang (1994). In stage 2, based on the well validated numerical model, the influence of unevenness on the support effect of shotcrete was further investigated.

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  • 32.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rockburst management at LKAB’s Kiirunavaara Mine: what can we learn from COVID-19 management2022In: Caving 2022: Fifth International Conference on Block and Sublevel Caving, Volume Two / [ed] Potvin, Y., Australian Centre for Geomechanics, 2022, p. 1135-1146Conference paper (Refereed)
    Abstract [en]

    Managing rockburst has been a challenging task in hard rock mines for many decades, and which still remains difficult especially when mining goes deeper. Since 2007, Kiirunavaara Mine has been identified as a seismically active mine and many severe rockbursts have occurred since then. Management of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection and treatment is also challenging in our society and we have been suffering from the wide-spreading of the coronavirus. Based on our recent studies, it isfound that there are many similarities between triggered rockburst and coronavirus infection. Considering the experiences obtained from coronavirus prevention and treatment, it is worthy of making a decent comparison of these two things and try to learn the lessons from COVID-19 management when thinking about rockburst management at LKAB’s Kiirunavaara Mine. This paper first reviews the chain of infection, pathophysiology of COVID-19, various preventative measures to reduce the chances of infection and current treatments after being infected with SARS-CoV-2. After that, the rockburst management at LKAB’s Kiirunavaara Mine is presented and compared with the COVID-19 management in terms of chain of dynamic interaction, damage mechanism, prevention or mitigation measures as well as treatment. Through the comparison, some suggestions are given regarding how to improve the present rockburst management at the Kiirunavaara Mine. Examples from recent studies in the mine are used to illustrate the improved understanding of the rockburst issues and improvement of the rockburst mitigation strategies. Discussion is presented on where further research or improvements would be conducted in the future.

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  • 33.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Botelho, Anneliese
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Woldemedhin, Biruk
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Field monitoring seismic response of underground excavations and rock bolts at kiirunavaara underground mine2019In: Rock Mechanics for Natural Resources and Infrastructure Development - Full Papers: Proceedings of the 14th International Congress on Rock Mechanics and Rock Engineering (ISRM 2019), September 13-18, 2019, Foz do Iguassu, Brazil / [ed] Sergio A.B. Fontoura; Ricardo Rocca; José Mendoza, Taylor & Francis, 2019, p. 1372-1379Conference paper (Refereed)
    Abstract [en]

    To assess the performance of underground excavations and ground support when subjected to mining-induced seismicity, a site has been instrumented at the Kiirunavaara mine. Geophones, multi-point extensometers and instrumented bolts were installed at the site. After the installation, several large seismic events (local magnitude>1.5) have occurred near the site and caused serious damages. The results from site monitoring indicate that the seismic waves are amplified near the excavation surface. The rock mass and rock bolts respond to mining-induced seismicity with step changes in displacement. The ejection velocity back-calculated from the energy absorbed in the rock bolts shows good agreement with the measured peak particle velocity (PPV). It is concluded that the scaling law used to evaluate the ground motion near excavation surface needs to be improved by considering velocity amplification. Repeated loading from multiple seismic events should be considered to assess rockburst damage.

  • 34.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Dineva, Savka
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Hansen-Haug, Jouni
    Lundin Mining.
    Woldemedhin, Biruk
    LKAB.
    Töyrä, Jimmy
    LKAB.
    Boskovic, Mirjana
    LKAB.
    Nyström, Anders
    Boliden.
    Marklund, Per-Ivar
    Boliden.
    Mozaffari, Shahram
    Boliden.
    Establishment of experimental sites in three Swedish mines to monitor the in-situ performance of ground support systems associated with mining-induced seismicity2016In: Proceedings of the 8th International Symposium on Ground Support in Mining and Underground Construction / [ed] E . N ordlund, T.H. Jones and A. Eitzenberger (eds), 2016Conference paper (Refereed)
    Abstract [en]

    In order to assess the performance of ground support components and systems when subjected to seismic activity and strong ground motion, Luleå University of Technology together with three Swedish mining companies (Lundin Mining, LKAB and Boliden) started a three year research project in September 2014. The aim of the project is to develop new methods for evaluating the rock support performance in-situ that use all available information about i) the source of the seismic event (obtained from the seismic network in the mine and additional seismic sensors), ii) seismic loading (ground motion) recorded by temporary local seismic networks, and iii) the consequences of the seismic loading in terms of damage to the underground excavations and the rock support.The sites with high potential of seismic damage were defined after the historical damaging seismic events were reviewed and the mining-induced stress disturbance was investigated with 3D numerical models. As of 31 December 2015, four sites in three different mines have been instrumented. Geophones (in depth and at surface), multi-points extensometers and instrumented bolts were installed to monitor the ground motion, the deformation of the rock mass and the elongation of the bolts. Observation boreholes were drilled to investigate the rock lithology, structures as well as fracture distribution and development. The data from locally installed geophones will be integrated with seismic data recorded by the mine-wide network. For each monitoring point, all of the instruments and observation boreholes were located at very close area within 0.5-1 m distance from each other. These results will be used to establish the relationship between the dynamic loading and the response of rock mass and rock bolts. Additionally, laser scanning is used to measure the surface deformation of the whole volume of instrumented sites with time. Two damaging seismic events occurred near the instrumented sites after the instruments were installed and the results of site investigation show that installed instruments have captured the response of the rock mass and bolts due to production blasting and seismic events.

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  • 35.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Eriksson, Fredrik
    Luleå University of Technology.
    Assessment of static performance of welded mesh along mesh overlap used at Kiirunavaara mine2023In: IOP Conference Series: Earth and Environmental Science / [ed] Lauri Uotinen, Erik Johansson, Institute of Physics (IOP) , 2023, Vol. 1124, no 1, article id 012093Conference paper (Refereed)
    Abstract [en]

    Localized failure of mesh, i.e., the mesh was cut or torn by rock blocks as a result of a seismic event, was observed at LKAB's Kiirunavaara mine. This is especially common along mesh overlap where mesh sheets are joined together. However, the performance of welded mesh along mesh overlap is not well understood. A series of tests was conducted at the laboratory at Luleå University of Technology, Sweden. The tested mesh sheets are made of 5.5 mm diameter wires welded along orthogonal directions spaced on a grid of 75 mm by 75 mm. The mesh sheet(s) was placed on a steel rig and fixed with bolts with spacing of 1.0 m by 1.0 m. A 300 mm loading plate made of concrete was placed underneath the mesh and pull/push load was applied on the mesh through the plate. For comparison purpose, the loading plate was placed at the mesh center following a dice five pattern as well as in the middle between two bolts (overlap position). The force-displacement curves of different test configurations were measured and failure modes of the mesh were observed. Laboratory test results show that the load-carrying and deformation capacity of the mesh is highly dependent on the load spreading and loading position relative to the holding points. When the mesh overlap was loaded, it shows: i) the highest stiffness; ii) the highest rupture load; iii) lower residual load-carrying capacity; and iv) the lowest deformation capacity. Two failure modes were observed in the conducted tests. Heat affected zone failure is the most common one and the second is the tensile failure along wires. Based on the laboratory results, an optimized mesh layout and bolting pattern was suggested for the Swedish underground mines.

  • 36.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering. College of Civil Engineering, Hunan University, Changsha 410082, China.
    Li, Ning
    Institute of Geotechnical Engineering, Xi’an University of Technology, Xi’an 710048, China.
    Li, Xi-bing
    School of Resources and Safety Engineering, Central South University, Changsha 410083, China.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Compressive failure model for brittle rocks by shear faulting and its evolution of strength components2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 5, p. 830-841Article in journal (Refereed)
    Abstract [en]

    A physical theory for brittle failure is presented that aims to explain both the phenomenological and micro-structural observations. The objective of this model is to capture the important attributes inferred from micro-structural experiments so as to arrive at constitutive relations that describe macroscopic failure behaviour. Based on experimental results, the micromechanical failure character- isation is summarised first. The localised failure process of rock will experience two stages: the brittle breakage stage (bond rupture of rock bridge) and the sliding stage (frictional resistance of failure plane mobilisation). A physical model is developed by dividing the sample into elastic and localised shear zones. Furthermore, the deformation process of the localised shear zone is divided into bond loss and frictional resistance mobilisation in two stages. To combine the micro-characteristics with the macromechanical properties, the chain models in localised shear zone, and the homogenisation method are adopted. The model is validated against the experimental data of Yumlu and Ozbay's. Subsequently, the localised progressive failure characteristics of rock are analysed by changing the model's parameters. The intrinsic effects and influential factors such as geometrical effects (size effect, shape effect), the strain softening phenomenon and Class II stress-strain curves are revealed. Finally, in order to be used easily by engineers, the simplified description of rock failure process and its evolution of strength components are given based on the model.

  • 37.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Ering
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    3DEC Numerical Analysis of the Interaction Between an Uneven Rock Surface and Shotcrete Lining2021In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 54, no 5, p. 2267-2289Article in journal (Refereed)
    Abstract [en]

    Rock tunnels excavated using drilling and blasting technique in jointed rock masses often have a very uneven and rough excavation surface. Experience from previous studies shows that the unevenness of a rock surface has a large impact on the support effect of shotcrete lining. However, clear conclusions regarding the effect of 2D and 3D uneven surfaces were not obtained due to limited studies in the literature. The numerical analyses reported in this paper were made to investigate the influence of the surface unevenness of a circular tunnel opening on the support effect of shotcrete using a 3D numerical code (3DEC). The models were first calibrated with the help of observations and measured data obtained from physical model tests. The influential factors were investigated further in this numerical study after calibration had been achieved. The numerical analyses show that, in general, the unevenness of a tunnel surface produces negative support effects due to stress concentrations in recesses (compressive) and at apexes (tensile) after excavation. However, shotcrete sprayed on a doubly waved uneven surface has better support effect compared to shotcrete sprayed on a simply waved tunnel surface. The development of shear strength (specifically frictional strength) on the uneven interface between the shotcrete and the rock contributes to this effect, in the condition where bonding of the shotcrete does not work effectively. The interface is a crucial element when the interaction between the rock and shotcrete is to be simulated. When an entire tunnel surface is covered by shotcrete with high modulus, more failures will occur in the shotcrete especially when rock surface is uneven. Based on the numerical model cases examined, some recommendations on how to incorporate tunnel surface conditions (2D or 3D unevenness) in the design of a shotcrete lining are given.

  • 38.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mikromechanical modeling of fire-induced thermal damae in a laboratory model tunnel2015Conference paper (Other academic)
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  • 39.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Numerical investigation of dynamic response of a rockbolt under drop testing and simulated seismic loading conditions2019In: Ground Support 2019: Proceedings of the Ninth International Symposium on Ground Support in Mining and Underground Construction / [ed] Hadjigeorgiou, J.; Hudyma, M., Australian Centre for Geomechanics, 2019, p. 387-398Conference paper (Refereed)
    Abstract [en]

    When designing rockbolts for rockburst conditions, it is commonly assumed that the kinetic energy of an ejected rock block is absorbed by rockbolts. To obtain the energy absorption capacity of a rockbolt, drop testing has been widely used. The advantage of using a drop test to investigate the dynamic performance of rockbolts is that it can provide repeatable results. However, it is recognised that the drop test technique is a crude simulation of an actual seismic loading mechanism. To investigate the difference, numerical models were constructed to simulate the response of a rockbolt under both drop testing and simulated seismic loading conditions using the numerical code UDEC (Universal Distinct Element Code, Ver 6.0) (Itasca Consulting Group 2018). The seismic wave is simplified as a full cycle sinusoidal wave which generates the same ejection velocity magnitude on a reinforced rock block as the drop test. The rockbolt was found to fail under the simulated seismic loading condition but survived the drop test. This difference is because reflected seismic waves create additional displacement between the ejected rock block and adjacent rock block. The results indicate that impact energy or kinetic energy should be used carefully when determining the dynamic demand on rockbolts as it does not consider the critical interaction between seismic waves and the reinforced rock blocks. Additional parameter sensitivity studies showed how the frequency of a simulated seismic wave affects the dynamic response of rockbolts. The results can be used to improve our understanding on the dynamic response characteristics of ground support. The knowledge gained from the comparison can be used to improve the estimation of dynamic demand on rockbolts under rockburst conditions.

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  • 40.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mainali, Ganesh
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saiang, Christine
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Jansson, Robert
    SP Sveriges Tekniska Forskningsinstitut.
    Experimental study of thermal spalling on rock blocks exposed to different fire/heating conditions2011In: Bergmekanikdag 2011: Föredrag, Stiftelsen bergteknisk forskning - Befo , 2011, p. 53-63Conference paper (Other academic)
  • 41.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mainali, Ganesh
    Saiang, Christine
    Jansson, Robert
    SP Technical Research Institute of Sweden.
    Adl-Zarrabi, Bijan
    SP Technical Research Institute of Sweden.
    Experimental study on thermal spalling of rock blocks exposed to fire2010In: Bergmekanikk i Norden 2010 = Rock mechanics in the Nordic countries 2010 / [ed] Charlie C. Li, Kongsberg, Norway, 9.-12. June 2010, 2010, p. 294-305Conference paper (Refereed)
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  • 42.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Swan, Graham
    Rock Mechanics and Mine Design, Sudbury, Canada.
    Yi, Changping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Velocity Amplification of Seismic Waves Through Parallel Fractures Near a Free Surface in Fractured Rock: A Theoretical Study2019In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, no 1, p. 199-213Article in journal (Refereed)
    Abstract [en]

    To determine the dynamic demand for support design under rockburst conditions, one of the most important issues is the prediction of ground motion parameters at the site of interest. Field monitoring has shown that the peak ground motion at the surface of an excavation in fractured rock is preferentially amplified compared to the motion in solid rock at a similar distance from the source. However, the traditional scaling laws used in rock support design do not account for the effect of free surface (excavation) and fracturing of rock. Recent studies have shown that high ground motion might be generated when a seismic wave crosses through fractures near a free surface in fractured rocks which is very complex and is not well understood. In this paper, particle velocity amplification was theoretically studied by investigating the dynamic interaction between seismic wave and multiple fractures near a free surface using the method of characteristics and the displacement discontinuity model. A harmonic load was applied on a model with a fractured zone near a free surface to investigate this phenomenon. After the harmonic wave propagated normally through multiple parallel fractures, the velocity amplification factor (VAF) was calculated as a function of the ratio of the magnitude of the peak particle velocity at the free surface of the model to the peak input velocity. The VAF can be as high as 3.77 and varies depending on the state of the fractured rock and the characteristics of the seismic wave. Parameter studies were conducted to investigate the effects of seismic load and multiple fractures on wave propagation, especially in terms of the wave frequency, the fracture spacing, the number of fractures and the stiffness of fractures. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion. Quantitative relationships between the various influential factors and the corresponding VAF were developed. It is anticipated that such relationships can provide criteria to improve the current design procedures and help mining engineers to improve their rock support practice for rockburst-prone areas.

  • 43.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Swan, Graham
    Rock Mechanics and Mine Design, Canada.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    1D numerical simulation of velocity amplification of P-waves travelling through fractured rock near a free surface2015In: Journal of the Southern African Institute of Mining and Metallurgy, ISSN 2225-6253, E-ISSN 2411-9717, Vol. 115, no 11, p. 1121-1126Article in journal (Refereed)
    Abstract [en]

    The most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four-to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time. In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0-3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion

  • 44.
    Zhang, Ping
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Yi, Changping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shirzadegan, Shahin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Nyberg, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Malmgren, Lars
    Mining Technology R and D, LKAB Kiruna Mine.
    Nordqvist, Anders
    LKAB.
    Numerical back-analysis of simulated rockburst field tests by using coupled numerical technique2013In: Ground Support 2013: Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction / [ed] Yves Potvin; B.G.H. Brady, Perth, Australia: Australian Center for Geomechanics , 2013, p. 565-581Conference paper (Refereed)
    Abstract [en]

    In order to assess the capacity of ground support systems when submitted to dynamic loading, simulated rockburst tests utilizing blasting have been performed for many years in different countries with limited success. In general, the blasts need to be carefully designed in order to reach the goal; however, different blast layouts (e.g. blasthole angle, burden) have been used based on researcher’s experience without conducting detailed analyses, the exception being a field test by CSIR. Recently, field trials have been conducted at the LKAB Kiirunavaara underground mine with some unexpected results which show that either the whole tested panel was destroyed or only a few fractures were formed without any ejections being observed. The aim of this paper is to investigate the failure mechanism in the simulated rockburst tests and improve the blast design by back-analyzing the test results using a coupled numerical modeling technique. The blast was simulated by using finite element method (LS-DYNA) and the dynamic interaction between the blasting generated waves and the opening was simulated by using discrete element modeling (UDEC) with the dynamic input from LS-DYNA. The numerical modeling showed that blasting can create both radial fractures radiating from the blasthole and fractures parallel or sub-parallel to the surface of the tested panel caused by reflected tensile stress waves. By comparing the results of the numerical modeling with the measured data, it is shown that the collapse failure was mainly controlled by the creation of a cone-shaped area formed by radial fractures and the burden seems to be a critical factor. In order to obtain fractures caused by reflected tensile stress waves and reduce blasting induced radial fractures, 2 parallel blastholes are suggested with larger burden (> 5 m) for future tests. Furthermore, the limitation of the current numerical modeling has also been discussed. The coupled numerical technique has shown its advantage when simulating blasting as well as interaction between waves and opening and it can thus be used as a tool for extrapolating results from simulated rockburst experiments if detailed geological structure and ground support system can be incorporated in the model and the model can be well calibrated.

  • 45.
    Zhang, Ping
    et al.
    Luleå University of Technology. Hunan University, China.
    Yin, J.J.
    Hunan University, China.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Li, N.
    Xi'an University of Technology, China.
    Determination and verification of the longitudinal deformation profile in a horse-shoe shaped tunnel using two-stage excavation2008In: MassMin 2008: Proceedings of the 5th International Conference and Exhibition on Mass Mining, Lulea, Sweden 9-11 June 2008 / [ed] Håkan Schunnesson; Erling Nordlund, Luleå: Luleå tekniska universitet, 2008, p. 845-854Conference paper (Refereed)
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  • 46.
    Zhang, Zhi-qiang
    et al.
    Xi’an University of Technology, Xi’an, P.R. China.
    Li, Ning
    Xi’an University of Technology, Xi’an, P.R. China.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Han, S.
    Xi’an University of Technology, Xi’an, P.R. China.
    Effect of fault on tunnel stability with different distribution2013In: Global View of Engineering Geology and the Environment: International Symposium & 9th Asian Regional Conference of IAEG / [ed] Faquan Wu; Shengwen Qi, London: CRC Press, Taylor & Francis Group , 2013, p. 279-285Conference paper (Refereed)
    Abstract [en]

    For tunnel engineering, the fault that locates near tunnel always plays an important role on the stability of the surrounding rock mass and the safety of the supporting system. To investigate the influence of the fault on the tunnel stability, systematic numerical experiments are carried out via the FINAL code. Through these numerical experiment results, the displacement and the distribution of the stress in surrounding rock mass are analyzed for these cases of the different locations and dips of fault around tunnel periphery, and the stress in the sprayed concrete layer are analyzed as well. To simulate the characteristics of the fault located in the rock mass, the COJO element, embedded in the FINAL code, is used in all numerical experiments. The quantized results reflecting the rules of the change for the displacement, stress, plastic region in the surrounding rock mass are obtained also in this paper.

  • 47.
    Zhang, Zhiqiang
    et al.
    Xi’an University of Technology, Xi’an, China.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Li, Yunxiang
    Xi’an University of Technology, Xi’an, China.
    Numerical Simulation of a Round Determinate Panel Test of Combined Concrete Panel and Welded Wire Mesh 2018In: Paper presented at the ISRM International Symposium - 10th Asian Rock Mechanics Symposium, Singapore, October 2018 / [ed] Z. Zhao; Y. Zhou; J. Shang, International Society for Rock Mechanics and Rock Engineering / Society for Rock Mechanics and Engineering Geology , 2018, article id ISRM-ARMS10-2018-146Conference paper (Refereed)
    Abstract [en]

    The sprayed concrete layer, together with external welded wire mesh, has been widely used as an important surface support in underground excavation in civil and mining engineering. Recently, the load carrying capability of combined concrete layer and welded wire mesh was evaluated by a round determinate panel (RDP) test. However, performance assessment by using RDP specimens is hindered by the testing boundary condition and the failure pattern and mechanism of combined concrete layer and welded wire mesh remains unclear. In this paper, the numerical model of the RDP test was set up by means of a FEM code, ABAQUS, and a series of numerical tests were carried out to investigate the failure mechanism and the influence of boundary condition on the performance of the RDP tests. To ensure the constitutive model of concrete embedded in ABAQUS and the material parameters were correctly used, the numerical models were first calibrated by the laboratory results with different concrete panel thickness without using welded wire mesh. After that, the performance of the combined concrete layer and welded wire mesh was examined by using the calibrated concrete model and mesh model and the failure mechanism of the combined specimens was obtained. The results show that the failure pattern matches the laboratory observation rather well and the peak load carrying capacity of the combined concrete layer and welded wire mesh panel is a little higher than that of the concrete only panel but the residual load carrying capacity has been improved. The boundary condition has large effect on the load-displacement curve, which is discussed in detail in the paper. The objective was to develop a numerical methodology which could be used to evaluate the load carrying capacity of combined concrete layer and welded wire mesh and thereby improve the assessment of the performance of shotcrete and welded wire mesh on site. 

  • 48.
    Zou, Yang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Zhang, Ping
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Assessment of energy release and redistribution on excavation instabilities for underground mining2023In: Proceedings of the 15th International ISRM Congress 2023  on Rock Mechanics and Rock Engineering & 72nd Geomechanics Colloquium: Challenges in Rock Mechanics and Rock Engineering / [ed] Schubert, W.; Kluckner, A., Austrian Society for Geomechanics , 2023, p. 313-318Conference paper (Refereed)
1 - 48 of 48
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