盾构法隧道地表变形影响因素多尺度数值模拟

采用三维非线性有限元数值方法,对上海典型地层中盾构推进过程进行了精细模拟,研究了多几何尺度下盾构外径、隧道埋深及土层力学性质等非施工因素对地表变形的影响。计算结果表明,盾构机外径的尺度效应和隧道埋深对地表变形影响显著;不同尺度下修正剑桥模型中与土性有关的对数硬化模量λ及泊松比μ与地表变形正相关,而临界状态有效应力比M与变形之间的关系不是单调增加或减小的关系。研究成果为软土地区盾构隧道多几何尺度的模型试验和设计施工参数的选取提供了依据。

Multi-scale Numerical Simulation on the Influencing Factors of Surface Deformations in Shield Tunneling

Based on multi-scale methodology, the influence of the shield diameter and embedded depth and soil properties on surface deformations is investigated using the 3D nonlinear finite element method. In the studies, the transversely isotropic property of tunnel lining, the shield machine, the void grout, the tunnel face pressure and so on are considered and the response of shield tunneling is analyzed. For shield-driven tunnels, the advancement of the step-by step tunnel construction process is modeled elaborately on the typical strata in Shanghai in this paper. The computed results show that the surface deformations are significantly affected by the dimension of shield diameter and embedded depth, and in general, the maximum surface displacement increases with increasing excavation diameter and decreasing tunnel axis depth; and are in positive correlation with the logarithmic hardening module λ and Poisson’s ratio μ under different scale conditions, while deformations have no monotone relationship with the stress ratio M in the elasto-plastic Cam-Clay model. The reasonable results provide valuable basis with regard to the scale model test and the selection of designing and construction parameters in shield tunneling.