IN-SITU TEST RESEARCH ON INFLUENCE OF EXCAVATION METHOD ON INDUCED DAMAGE ZONE IN DEEP TUNNEL
YAN Peng1，2，3，LU Wenbo1，2，CHEN Ming1，2，SHAN Zhigang3，CHEN Xiangrong3
(1. State Key Laboratory of Water Resources and Hydropower Engineering Science，Wuhan University，Wuhan，Hubei 430072，China；2. Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of Ministry of Education，Wuhan University，Wuhan，Hubei 430072，China；3. HydroChina Huadong Engineering Corporation，Hangzhou，Zhejiang 310014，China)
Abstract：Different stress paths of surrounding rock corresponding to different excavation methods，such as blasting or tunnel boring machine(TBM)，have important influence on the formation of excavation damage zone during construction of deep tunnel. However，the influence has not yet attracted enough attention. Based on the excavation in deep tunnel group of Jinping II hydropower station，the characters and formation factors of damage zones under different excavation methods are discussed by field detecting test；and extents of damage zone induced by in-situ stress transient or quasi-static adjusting are calculated by using numerical simulation method；and the basic mechanical characters of Jinping marble and in-situ stress transient adjusting effect are considered in the calculation. The test results show that the depth of inner damage zone(severely damaged zone) in blasting excavation tunnel accounts for more than 50% of the total damage zone depths；and the rock in this area have been damaged seriously and lost its bearing capacity. The distribution of inner damage zone in the tunnel section is seriously influenced by redistribution stress field，which can be regarded as the evidence of that the in-situ stress transient adjusting effect is one of the direct causes of damage zone formation. In the tunnels excavated by TBM method，the inner damage zone only accounts for 30% of the total damage zone depths；and the formation of this area could be mostly attributed to the time effect of the strength of Jinping marble. It is the result of improvement of stress relaxation at tunnel surface. After considering the mechanical characters of brittle-extension-plastic of marble and transient adjusting effect of in-situ stress，the extents of excavation damage zones under different excavation stress paths can be estimated objectively using numerical simulation method. The conclusion of this paper has important significance for the selection of excavation method and support measures of deep tunnel.
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YAN Peng1，2，3，LU Wenbo1，2，CHEN Ming1，2，SHAN Zhigang3，CHEN Xiangrong3. IN-SITU TEST RESEARCH ON INFLUENCE OF EXCAVATION METHOD ON INDUCED DAMAGE ZONE IN DEEP TUNNEL. , 2011, 30(6): 1097-1106.
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2011, Vol. 30 
