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| STUDY OF FAILURE BEHAVIOR OF DEEP HARD ROCK UNDER POLYAXIAL STRESS CONDITIONS |
| PAN Pengzhi，FENG Xiating，QIU Shili，ZHOU Hui |
| (State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China) |
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Abstract Based on the failure behavior of deep hard rock and group works，a rock mass local deterioration model(RLDM) is developed to reflect the evolution of deformation and strength parameters of rocks with plastic variables under polyaxial stress conditions. The model is integrated into a self-developed three dimensional elastoplastic cellular automaton(EPCA). The cellular automaton technique，which is based on the localization theory，is convenient to perform the dynamic updating of local mechanical parameters. The EPCA code with RLDM is used to study the influence of polyaxial stress on failure behavior of rock specimens in laboratory and in-situ deep diversion tunnel of Jinping II hydropower station. The modeled complete stress-strain curves of rocks under triaxial compression can well reflect the transition from brittle failure to ductile failure of rocks；the curves are agreement with experimental phenomenon. The modeled failure mode of Jinping II diversion tunnel well reflects the actual failure mechanism. Based on the calibrations of the model and numerical method，it is used to simulate the failure behaviors of deep hard rock tunnels by considering different lateral stress coefficients and different intermediate principal stresses and their directions. Influence of polyaxial stress on fracture of deep hard rock is analyzed；and causes of complex failure modes of deep hard rock tunnels are also explained. It is concluded that，the increase of minor principal stress increases the stability of the tunnel. The stability of deep tunnel shows the phenomenon of intermediate principal stress effect and interval characteristics.
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Received: 14 February 2011
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2011, Vol. 30 
