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| Compression failure characteristics and crack propagation of brittle rock under various confining pressures#br# |
| MA Wenqiang1，WANG Tongxu2 |
(1. College of Architecture and Civil Engineering，Xinyang Normal University，Xinyang，Henan 464000，China；
2. State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology，Shandong University of Science and Technology，Qingdao，Shandong 266510，China)
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Abstract To reveal the failure characteristics and crack propagation law of brittle rock under triaxial compression，mechanical parameters and deformation-failure characteristics of oil shale were obtained through laboratory compression tests under various confining pressures first. Based on the Voronoi block division logic，Fish language was used to compile a program，and a numerical model composed of trigon blocks was established in UDEC with the program. The micro-parameters was determined through calibrating properties，and an optimal trigon edge length average was chosen to construct standard compression numerical specimens. A series of compression simulations under various confining pressures were performed. According to the contact failure criterion，some FISH programs were compiled to calculate the number and length of contacts which broke in the compression process through iterations. The failure of contacts represents crack initiation and propagation，the compressive failure modes and crack development law were gained at last. It turns out that the shear angle increases slightly with the increasing of confining pressure，and the failure mode is brittle shear containing a set of conjugate shear planes，which is in agreement with numerical simulation results. The shear failure plays the main role in triaxial compression. For the same specimen，the number of shear cracks is 6 times of the tensile cracks，while the length of shear cracks are 40–70 times of the tensile cracks. With the increasing of confining pressure，the maximum length of shear cracks increase gradually from 77.3% to 94%，but the maximum length of the tensile cracks decrease from 16.3% to 12.1%.
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2018, Vol. 37 
