Numerical simulation of a jointed rock block mechanical behavior adjacent to an underground excavation and comparison with physical model test results |
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| Affiliation: | 1. State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221008, China;2. Rock Mass Modeling and Computational Rock Mechanics Laboratories, University of Arizona, Tucson, AZ 85721, USA;1. Department of Civil Engineering, Monash University, Building 60, Clayton, VIC 3800, Australia;2. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore;1. School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China;2. Faculty of Land Resources Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China;1. School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;2. State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining & Technology, Xuzhou 221116, China;3. College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China;1. School of Resources and Safety Engineering, Central South University, Changsha, Hunan 410083, China;2. School of Civil, Environmental and Mining Engineering, The University of Western Australia, Perth 6009, Australia;1. School of Architecture and Civil Engineering, Nantong University, Nantong 226019, China;2. School of Civil, Environmental and Mining Engineering, The University of Adelaide, SA 5005, Australia;1. State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, PR China;2. Deep Earth Energy Research Laboratory, Department of Civil Engineering, Monash University, Melbourne, VIC 3800, Australia |
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| Abstract: | Mechanical behavior of a jointed rock mass with non-persistent joints located adjacent to a free surface on the wall of an excavation was simulated under without and with support stress on the free surface using approximately 0.5 m cubical synthetic jointed rock blocks having 9 non-persistent joints of length 0.5 m, width 0.1 m and a certain orientation arranged in an en echelon and a symmetrical pattern using PFC3D software package. The joint orientation was changed from one block to another to study the effect of joint orientation on strength, deformability and failure modes of the jointed blocks. First the micro-mechanical parameters of the PFC3D model were calibrated using the macro mechanical properties of the synthetic intact standard cylindrical specimens and macro mechanical properties of a limited number of physical experiments performed on synthetic jointed rock blocks of approximately 0.5 m cubes. Under no support stress, the synthetic jointed rock blocks exhibited the same three failure modes: (a) intact rock failure, (b) step-path failure and (c) planar failure under both physical experiments and numerical simulations for different orientations. The jointed blocks which failed under intact rock failure mode and planar or step-path failure mode produced high and low jointed block strengths, respectively. Three phases of convergence of free surface were discovered. The joint orientation and support stress played important roles on convergence magnitude. The average increment of jointed block strength turned out to be about 10, 7.9 and 6.6 times the support stress when support stresses of 0.06 MPa, 0.20 MPa and 0.40 MPa were applied, respectively. The modeling results offer some guideline in support design for underground excavations. |
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| Keywords: | Mechanical behavior Non-persistent joints Jointed rock Underground excavations |
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