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Abstract The damage caused by TBM excavation is slighter than that by drilling and blasting method. The hollow inclusion stress gauge near the excavation profile cannot be easily damaged. So the hollow inclusion stress gauge can be embedded in designed position of surrounding rock in advance to monitor the stress evolution during TBM driving. Firstly，in order to analyze the tunnel face effect and crack initiation strength of surrounding rock，and confirm the ranges of relaxation zone and damage zone，the stress redistribution after tunnel excavation is calculated by numerical method. Due to the above research results，the embedded position and monitoring start time are both ensured. Secondly，the hollow inclusion stress gauges are installed by drilling from test tunnel to TBM driving tunnel and embedded in relaxation zone and damage zone of the tunnel separately；and the entire process of stress from start changing to be stable is also monitored. The monitoring results affirm the existence of tunnel face effect and show that the stress begins to vary from the one time of tunnel diameter of anterior tunnel face. The region of half of tunnel diameter of posterior tunnel face is the most violent stress redistribution area. The damage zone scope is analyzed through crack propagation sensitivity by hollow inclusion stress gauge. The crack initiation strength of surrounding rock is verified by the monitoring results which well meet the numerical calculation results. The research results can provide references for confirming damage zone scope and crack initiation strength of rock mass. The results can also provide scientific basis for supporting design and selection of supporting time.
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Received: 20 May 2011
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2011, Vol. 30 
