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Abstract TBM is known for its quick driving，but the normal driving will be affected under the unfavorable geological condition because of the limitation of equipment and the supporting capacity. TBM faces the risk of lock and even shutdown. The general depth of Jinping II diversion tunnel is more than 1 500 m，and the geological condition is very complex. When TBM driving in unfavorable geological period of Baishan group，due to the low strength of broken surrounding rock，and the poor steady ability，the risk of TBM driving need to be evaluated. First the initial mechanical parameters of rock mass were studied by excavation response of field surrounding rock. Then，comparing the displacement of different quality of rock mass and the thrust needed for TBM driving，it was found that the required thrust in the unfavorable geological condition has exceeded the provide maximum thrust，and that the displacement is also hard to limit in the range of TBM expansion. The surrounding rock has been damaged in gripper compression，and cannot provide enough thrust to ensure TBM driving. The pilot tunnel was proposed，and the calculation results show that the pilot tunnel can relieve deformation to avoid lock. Other support optimization designs and coping strategies were presented. The research results can provide good reference for similar engineerings.
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2015, Vol. 34 
