岩体地下工程局部围岩失稳的能量耗散突变判据

Instability criterion for judging energy dissipation catastrophe of local rock mass system of underground engineering

岩体地下工程的围岩稳定评判具有复杂的非线性特征,目前尚无确定性方法量化描述局部岩体系统的塑性失稳过程.在阐释开挖扰动与局部岩体系统失稳概念的基础上,借助突变理论,提出了岩体地下工程局部围岩系统开挖失稳的能量耗散突变判据.根据能量耗散原理及弹塑性有限元算法,定义了塑性耗散能密度(PDED)和表征耗散能(RPDE)的概念.通过表征耗散能突变特征值D判断系统失稳的状态,通过单元塑性耗散能密度的分布情况判断引起失稳的大致局部部位以及塑性破坏的可能程度.对锦屏一级水电站大型地下洞室群施工开挖过程进行了稳定分析,结果表明,该判据能够量化反映洞室局部围岩系统失稳的行为过程,与工程实践较为吻合,具有一定的工程参考价值.

Stability assessment of surrounding rock of underground engineering is complicated with complex nonlinear characteristics;while a deterministic method to describe the stability status of local rock mass system hasn＇t been proposed.Therefore,based on catastrophe theory,an instability criterion for judging energy dissipation catastrophe of local rock mass system of large-scale underground excavations is put forward after the explanation of the concepts of excavation disturbed effect and local rock mass instability.Then,plastic dissipative energy density（PDED） and representative plastic dissipative energy（RPDE） are defined on the basis of energy dissipation principle.The criterion is used to judge the stability status of local rock mass system through catastrophe eigenvalue D of RPDE and determine the local damage position that results in instability.Finally,a case study is further illustrated with the simulation of excavation of a large-scale underground caverns group of Jinping I hydropower station;and it is shown that the criterion can reflect the instable behavior of surrounding rock system and satisfy engineering excavation practice,which is valuably referenced for underground excavation.