以佛-莞城际线路长隆隧道工程为背景,采用室内试验和数值模拟,研究常压开仓时换刀区失稳和渐进破坏过程.结合工程实际建立数值模型,采用快速拉格朗日差分法分析钢管桩-注浆方案常压换刀区地层的安全系数,对比分析钢管桩-注浆加固方案对换刀区地层应力释放和位移的控制效果.结果表明,常压开仓时盾构开挖面首先失稳,并引起土体流失以及土压力释放现象;随着刀盘后移,逐渐诱导换刀区地层出现大范围竖向位移,最终贯通至地表.采用钢管桩-注浆方案,换刀区安全系数得到显著提高,地层应力释放和位移均得到有效控制.与注浆加固方案相比,钢管桩-注浆方案具有工期短、污染少的优点且钢管桩可回收,不影响土体后续使用,为工程提供新的地层加固思路.

Based on the Foshan-Dongguan Intercity Line Changlong Tunnel Project, indoor tests and numerical simulations were conducted to study the instability and progressive failure process of the cutter replacement ground at atmospheric pressure. The fast Lagrangian analysis of continua method was adopted to establish the numerical model. The safety factor of the cutter replacement ground was analyzed, and the effect of the steel pipe pile-grouting method on the control effect of release and displacement was studied. The results show that the excavation face becomes unstable at atmospheric pressure, which causes soil loss and earth pressure release. As the cutter head moves backward, a large-scale vertical displacement of cutter replacement ground is gradually induced, and finally goes through to the surface. With the steel pipe pile-grouting reinforcement, the safety factor of the cutter replacement ground is significantly improved, and the ground stress release and displacement is effectively controlled. Compared with the grouting reinforcement, the steel pipe pile-grouting reinforcement has the advantages of short construction period and less pollution. Moreover, the steel pipe pile could be recycled without affecting the subsequent use of the soil, which provides a new ground reinforcement idea for the project.