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  • 1.
    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)
  • 2.
    Shirzadegan, Shahin
    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 support2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increasing mining depth leads to higher stress magnitudes, resulting in increased seismic activity and more seismically-induced damage. The effectiveness of the ground support system under dynamic loading conditions has therefore become of prime interest to the mining companies in order to provide safe mining conditions with a minimum of production disturbances caused by unstable infrastructure. The problems of mining-induced seismicity have necessitated the use of ground support systems which are capable of withstanding strong dynamic loads. Although there are large amounts of measurement data from the site-installed seismic systems, they cannot be used directly to design and select the appropriate support systems due to lack of control over the location and nature of the seismic source and the effect of the rock mass on the seismic waves. Large-scale tests using explosives as the seismic source have therefore become a useful method to evaluate the performance of rock support systems for seismic conditions. A series of seven large scale dynamic tests of rock support was conducted in the Kiirunavaara mine. Explosives were detonated in boreholes in the pillar between two cross-cuts in order to generate a dynamic load on the rock support system installed on the cross-cut wall. This was done with the aim to develop a testing methodology for in-situ testing of ground support. Furthermore, the response of the installed support system to strong dynamic loading was also evaluated. The tests included ground motion measurements, fracture investigation, ground and support motion imaging, as well as the deformation measurements. The results of the measurements in Tests 1 to 7 are presented and the methodology used to design the tests is discussed. The results indicated that the relation between the burden distance and the used amount of explosive material and number of blastholes has a vital role in either reducing or involving the effect of detonation gases in test results. The large amount of data recorded during these tests will be useful for the calibration of more advanced numerical models. The energy absorption by the Swellex Mn24, 100 mm fibre reinforced shotcrete (40 kg/m3 steel fibre) and 75 mm x 75 mm weld mesh with 5.5 mm diameter was estimated and compared to that obtained from the large scale in-situ tests and laboratory tests conducted in different countries. The comprehensive ground motion data provided for the whole test wall was used to estimate the kinetic energy transmitted to the fractured zone where the support system was installed.

  • 3.
    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.

  • 4. Shirzadegan, Shahin
    et al.
    Nordlund, Erling
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Villegas, Tomas
    Numerical analyses of the effect of larger-scale geological structures on the hangingwall subsidence at Kiirunavaara mine2010Conference paper (Other academic)
    Abstract [en]

    The current mining method, sublevel caving at the Kiirunavaara iron ore mine, has induced large scale subsidence to the hangingwall. The orebody dips, on average, 60° eastward. Therefore the subsidence is developing toward the city of Kiruna, the railway and other infrastructure. One of the most important factors which can affect the hangingwall subsidence is the existence of large-scale geological structures in the hangingwall. The 2D distinct element code UDEC was used in this work to evaluate the effect of geological structures on the hangingwall subsidence. One so called "basic model" was run without any geological structures. One structure set with the dip in the interval 50° - 90° to the east has been then analyzed. The failure surface at each mining level was defined for the different models through failure indicators e.g. yielded elements in shear and tension and surface critical vertical displacement. To evaluate the effect of each orientation on the hangingwall subsidence, the break angle was calculated at each mining level. The results showed that inclined structures had an obvious effect on the extension of the failure surface on the hangingwall. All models with large-scale structures showed a decrease of the break angle compared to the basic model. The structure orientations showed a tendency to govern the direction of shear and tensile failure in the models. The results indicate that it is important to identify the dominating structures and their orientation and the structural geological domains. Keywords: Numerical analysis, Geological structures, failure surface, Break angle.

  • 5.
    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.

  • 6.
    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

  • 7.
    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.

  • 8.
    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.

  • 9.
    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)
  • 10.
    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)
  • 11.
    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)
  • 12.
    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)
  • 13.
    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.

  • 14.
    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.

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