岩体开挖松弛的判据与有限元分析

Relaxation criterion and finite element analysis of rock mass excavation

针对地下洞室、边坡、大坝坝基等开挖过程中存在的岩体松弛问题,基于岩体开挖松弛机理,采用主拉应变准则作为松弛判据,提出了相应的松弛效应有限元算法,并以小湾工程坝基松弛问题为例进行了分析.该方法不但可以明确判断松弛发生的部位、范围和严重程度,而且能够对松弛后岩体内部的应力应变状态进行合理描述.研究结果表明:小湾工程松弛区范围及松弛后应力应变状态与现场监测成果符合较好,表明所采用的研究方法对高地应力地区开挖松弛问题是可行的.

In light of the rock mass relaxation phenomenon induced by excavation of underground cavern, slope and dam foundation, based on the relaxation mechanism of rock excavation, a criterion of maximum principal strain for pinpointing relaxation region is put forward, and a corresponding finite element algorithm for the evaluation of the relaxation effect is established. The relaxation phenomenon in Xiaowan arch dam project is taken as an example for the validation of the proposed criterion and algorithm. The method in this study can not only make quantity calibration of relaxation region and its damage degree, but also give a reasonable description of the stress and strain state in rock mass after relaxation. The results of calculation in Xiaowan project show good agreement with the field investigation in the aspect of relaxation region and stress and strain state. And the results also demonstrate that the method presented in this study has important potentiality for the rock relaxation problems during excavation in high terrestrial stress region.