南京地铁越江隧道盾构开挖面失稳因素的定量分析

Quantitative Analysis of the Factors Affecting the Face Instability of a River-Crossing Shield Tunnel of the Nanjing Metro

文章通过对造成盾构施工中开挖面失稳风险因素的系统分析,认为造成开挖面沉降过大或坍塌失稳的主要原因是泥水压力偏离实际的侧向静止水土压力过大。针对这个问题,引入了极限应力支护比的概念,并给出了失稳判据,定量地描述各影响因素对开挖面稳定性的影响情况。以南京地铁10号线越江隧道为工程实例,采用岩土工程常用的Mohr-Coulomb模型,运用三维数值分析方法,主要研究分析了埋深、江水深度、土体参数(粘聚力、内摩擦角)对开挖面稳定性的影响,以及考虑无江水覆盖情况下改变为地下水头高度的影响。

By way of systematic analysis of the risk factors resulting in instability of the tunnel face during shield construction, it was found that large deviation of the slurry pressure from the actual lateral static water-soil pressure is the main reason for large settlement or collapse at the working face. The concept of an ultimate support stress ratio and the judgment criteria for instability are presented and a quantitative description concerning the factors affecting the stability of the tunnel face is carried out. Using the river-crossing tunnel of the Nanjing Metro line l0 as an example, the affects of buried depth, river depth, and soil parameters （cohesion, internal friction angle） on the instability of the working face are studied by a Mohr-Coulomb model, which is commonly used in geotechnical engineering, and a 3D numerical analysis method. Considering the river water, the influence of varied groundwater head heights is also studied