(1. Institute of Geotechnical Engineering，Zhejiang University，Hangzhou，Zhejiang 310058，China；2. Key Laboratory of Soft Soils and Geoenvironmental Engineering of Ministry of Education，Zhejiang University，Hangzhou，Zhejiang 310058，China；3. Shenzhen Municipal Engineering Corp，Shenzhen，Guangdong 518034，China)
Abstract：In shield-driven tunnel，too large support pressure may lead to the upheaval of ground surface，even blow-out failure of tunnel face. In order to reveal the mechanism of blow-out failure and to obtain the limit supporting force，based on Mohr-Coulomb model，the blow-out failure of shield tunnels in sand is simulated using ABAQUS. Accordingly，the prism part of three-dimensional wedge model，which is based on limit equilibrium method，is modified to an inverted truncated pyramid，which is consistent with the actual upheaval zone better. The formulas of limit supporting force with regard to the angle of wedge are deduced. The minimum value，which is obtained by trial calculation，is the limit supporting force. The results obtained from the modified limit equilibrium model are well consistent with the numerical simulations results，and just fall in upper and lower bound solutions calculated by E. Leca et al. The model will provide reference for determining the upper value of supporting force of shield tunnels in sand.
MOLLON G，DIAS D，SOUBRA A H. Rotational failure mechanisms for the face stability analysis of tunnels driven by a pressurized shield[J]. International Journal for Numerical and Analytical Methods in Geomechanics，2010，35(12)：1363-1 388.
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2013, Vol. 32 
