Stability analysis of excavation face of shield tunnel in upper soft and lower hard composite strata
Aiming at the stability of shield tunnel excavation face under the condition of upper soft and lower hard composite strata,and according to the actual working conditions of Shenzhen-Huizhou Intercity Railway Section 2,the influence of different soft-hard ratios and soil parameters on the ultimate support pressure of excavation face was analyzed.The instability mode of soil was analyzed by using particle flow code(PFC)simulations,and a theoretical calculation model consistent with the instability profile of the excavation face was established by using limit analysis method.The theoretical calculation results were compared and analyzed with previous literatures and practical engineering.The results show that the deformation is mainly concentrated in the soft soil when the tunnel excavation face actively loses stability,whereas the deformation of hard rock is comparatively minor.As the soft-hard ratio of excavation face increases,the ultimate support pressure of tunnel excavation face also increases.In addition,the ultimate support pressure of excavation face is independent of the tunnel burial depth ratio but inversely proportional to the internal friction angle of the soil.
shield tunneldiscrete elementupper soft and lower hard composite stratalimit analysis methodexcavation face stabilityburial depth ratiointernal friction anglesoft-hard ratio
万方数据
维普
