临近隧道基坑开挖中土体加固的敏感性分析

Reinforcement sensitivity of soil during excavating of foundation pit being adjacent to tunnels

结合某软土地区基坑开挖对邻近隧道纵向影响保护方案,利用ABAQUS动态模拟基坑开挖对临近隧道纵向变形及隧道断面弯矩的影响,对比分析坑内三轴搅拌桩土体加固强度与加固深度作为保护方案的敏感性。分析得出:随着加固强度的增加,隧道纵向位移有显著减少,达到一定值后,约束作用明显减弱;加固强度的增加对隧道纵向截面弯矩影响较弱;加固深度对隧道的变形有明显的抑制作用,但并非加固深度越深越好;地下连续墙、被动土体加固对临近基坑开挖引起的位移具有阻断作用;针对本案例,提出最优加固强度200 MPa及加固深度6 m,这既能对隧道变形起到很好抑制作用,又能实现最优的经济效益。

Based protection scheme of longitudinal impact of the excavation on the adjacent tunnel in soft soil, the influence of foundation pit excavation beng adjacent to tunnel on longitudinal displace- ment and moment was systematically analyzed by using ABAQUS. Three shaft stirring pile was taken as protection scheme sensitivity by making comparisons between strength and depth of reinforcement. After comparison, it is found that the longitudinal displacement decreased obviously with increasing of reinforcement intension, and restriction effect decreased obviously when the longitudinal displacement reached certain value. The increase of reinforcement intension had little weaker effect on the longitu- dinal section monment. The reinforcement depth had obvious effect on the distortion of tunnel, but the big reinforcement depth was not optimal. The diaphragm wall and the passive soil reinforcement had blocking effect on the displacement caused by foundation pit excavation being adjacent to tunnel. In this study, the optimal reinforcement intension was 200 MPa and the reinforcement depth was 6 m, which can have good effect on the tunnel distortion and reach the good economical benefit.