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| A MICRO PARTICLE MODEL FOR HARD BRITTLE ROCK AND THE EFFECT OF UNLOADING ROCK BURST |
| MA Chunchi，LI Tianbin，CHENG Guoqing，CHENG Ziquan |
(State Key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，
Chengdu，Sichuan 610059，China) |
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Abstract A bonding particle model for hard brittle rock has been established to simulate the effect of rock burst. To make the microscopic model reflecting properties of hardness and brittleness，the following steps were used. Firstly，the microstructure of simulated rock samples was measured with the X-ray diffraction testing for granite rock. Secondly，the mechanical properties of the rock samples were analyzed, supported with the evaluation indicators of hardness and brittleness(indicators were determined in terms of the energy and stress-strain characteristics). Finally，a visual framework of the bonding particle model(depending on the tendency and magnitude limitation of the existed microstructure，the parameters of particles and bonds) representing the properties of hardness and brittleness was established. The model and the particle flow code(PFC3D) were used to simulate the triaxial unloading test and to analyze the effect of rock burst. The fractures are found to be mainly tensile in the unloading tests with the low and high confining pressures. Bigger proportion of tensile fractures and larger stress dropping(more brittle) occurs under the high confining pressure than under the low confining pressure. The kinetic energy of particles under the low confining pressure develops uniformly in the whole fracturing process of simulated sample，and the rock burst is a continuous type. However，the kinetic energy of particles under the high confining pressure developed non-uniformly，and the rock burst occurred suddenly and explosively.
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Received: 08 April 2014
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2015, Vol. 34 
