隧道开挖对邻近土体位移影响的数值分析

在城市修建地铁的过程中，隧道洞口开挖会不可避免地对隧道洞口周围的土体产生影响。采用有限差分软件FLAC3D来分析由于隧道开挖而引起的土体位移。在数值模型中，假设衬砌为线弹性材料；而土体则是由Mohr--Coulomb破坏准则控制的弹塑性材料。将采用有限差分软件计算得到的土体位移结果同采用解析法以及经验法得到的位移结果进行对比。并结合不同土层刚度以及衬砌刚度的情况，来分析以上两个因素对土体位移的影响。经过分析得到的结果表明：（1）通过有限差分软件计算得到的地表土体沉降曲线能够与采用解析法以及经验法得到的沉降曲线很好的吻合，但是采用数值方法得到的沉降曲线相对较宽并且较浅。（2）在上软下硬土层中，地表土体的最大沉降值将变大而沉降曲线将变窄；而在上硬下软土层中，地表土体的最大沉降值将变小而沉降曲线将变宽。（3）随着衬砌刚度的增大，土体的位移将会减小。

Numerical analyses of tunnel-induced soil movements

It is inevitable that tunneling under the ground will cause ground movement. The finite difference analysis software FLAC3D was used to study the soil movements caused by tunneling. The model was calculated on the assumption that concrete lining was elastic. And soil which was ruled by Mohr--Coulomb failure criteria was assumed to be elastic-plastic. The answers which were given by the finite difference analysis software FLAC3D were compared with those given by analytical method and empirical method. The change of soil stiffness and concrete lining stiffness was also considered in this paper. The results which were given by the numerical model indicate that： （1）The surface settle- ment trough given by FLAC3D met well with the other two methods, but the settlement trough was a little wider and shallower. （2）The surface settlement in upper soft and lower hard strata got larger and the settlement trough became narrower; while the surface settlement in upper hard and lower soft strata got smaller and the settlement trough became larger. （3）The soil displacements may decrease with the increasing of concrete lining stiffness.