基于Mohr-Coulomb准则的应变软化浅埋隧道围岩弹塑性解

Elasto-plastic solution of shallow tunnel considering strain-softening characteristics based on Mohr-Coulomb criterion

针对软化围岩浅埋隧道开挖问题,提出一种弹塑性半解析解,确定半无限空间下塑性区范围和应力位移分布。具体的方法分为:对Verruijt等提出的弹性解进行修正,结合弹塑性交界面上应力连续原则,得到塑性区外边界上应力和应变;采用Zou等提出的逐步半径增量法从外向内推导塑性区应力应变;若计算出的塑性区内边界径向应变等于隧道壁应变,则可以确定塑性区,应力和位移,利用数值模拟解验证本文方法的可靠性。研究结果表明:浅埋隧道不同方向的塑性区半径不同,拱顶方向最大,拱底方向最小。

In this paper,an elasto-plastic semi-analytical solution was proposed.The plastic zone and distribution of stress and displacement in semi-infinite space was determined.The specific method was divided into three steps:The elastic solution proposed by Verruijt in the semi-infinite space was modified,and the stress and strain on the outer boundary of the plastic zone were obtained by combining the principle of stress continuity on the elasto-plastic interface.The stress and strain of the plastic zone were derived from the outside to the inside by the stepwise radius increment method presented by Zou.If the calculated radial strain in the plastic zone is equal to the tunnel wall strain,the plastic zone,stress and displacement can be determined.The reliability of the method was verified by numerical simulation.The results show that the plastic radiuses of the shallow tunnel in different directions are different.