【摘要】 依托徐州市轨道交通2号线一期工程周庄站—七里沟站区间盾构隧道工程，应用数值模拟法，进行上软下硬复合地层中盾构隧道开挖面变形特性和破坏模式分析；假定上软下硬地层中盾构隧道开挖面失稳模式为部分梯形楔形体，借助极限平衡理论，推导开挖面极限支护压力计算式，并基于松动土压力理论建立均质土和成层土上覆土压力计算式。结果表明：当上软下硬地层弹性模量比值较大时，盾构隧道开挖面失稳为发生在上部软土层中的局部破坏，而当比值较小时，开挖面失稳为整体破坏；当依托工程上部软土层厚度超过1.5 m时，隧道开挖面将发生失稳破坏；采取注浆加固的处理措施，能确保依托工程现场施工安全。更多还原

【Abstract】 Based on the interval shield tunnel engineering between Zhouzhuang Station and Qiligou Station of the first-stage project of Xuzhou Rail Transit Line 2, the deformation characteristics and destruction mode analyses of the excavation surface of the shield tunnel in the upper-soft and lower-hard composite strata are carried out by numerical simulations. Assuming the instability mode of the excavation surface of the shield tunnel in the uppersoft and lower-hard strata is a partially trapezoidal wedge, the calculation formula for the limit support pressure of the excavation surface based on limit equilibrium theory is derived and that for the overlying soil pressure in isotropic soil and stratified soil is established based on loose earth pressure theory. The results show that the instability of the excavation surface of the shield tunnel reveals to be local failure in the upper-soft strata when the ratio of the elasticity modulus of the upper-soft and lower-hard strata is larger; while overall failure will occur when the ratio is smaller. The instability failure of the tunnel excavation surface will occur when the thickness of the upper-soft strata of the supporting project exceeds 1. 5 m. On-site construction safety of the supporting project can be ensured by using grouting consolidation for treatment measures.更多还原