低地应力区地下洞室围岩变形破坏有限元数值模拟研究

SIMULATION OF DEFORMATION AND FAILURE OF SURROUNDING ROCK MASSES OF UNDERGROUND CAVERN IN LOW GROUND STRESS REGIONS WITH FINITE ELEMENT METHOD

低地应力状态对相关工程岩体变形破坏和稳定性有重要影响,以西安市黑河水利地下工程泄洪洞为例,采用弹塑性二维有限元法通过对低地应力区地下洞室开挖后围岩变形破坏进行了数值模拟研究。模拟结果表明:低地应力区洞室围岩变形破坏主要发生在垂直方向,水平方向的规模和程度均不及前者,同时总结分析了低地应力区地下洞室开挖后围岩变形破坏规律及其特征。该项研究工作将有利于进一步研究低地应力区地下洞室围岩变形破坏机理与稳定性,它对保障地下洞室工程的顺利进行起到积极促进作用,具有重要的理论研究价值和现实意义。

The low ground stress state has great influence on the features of deformation, failure and stability of rock masses in such stress state. In this paper, 2D elastoplastic finite element method (FEM) is used to simulate the whole deformation and failure process of surrounding rock masses of the underground cavern project of Heihe River Reservoir in Xi'an city. The rock masses are in the low ground stress regions and belong to class IV according the code of rock mass quality classification. The established computational model consists of 5 kinds of stratum elements. According to the stress distribution characteristics in the low ground stress regions, the boundary conditions of the computational model are determined. The FEM software 2D-σ is used to conduct the numerical simulation. The adopted physical and mechanical material parameters are obtained by tests. The characteristics of whole process of surrounding rock mass deformation and failure have been simulated. The simulation results show that the deformation and failure will be formed at the vault and both sides of underground cavern; and the deformation and failure of surrounding rock masses at the vault are more serious than those at both sides. These results agree well with the real cases. The achieved results will be of great significance for the further study of deformation and failure mechanism of surrounding rock masses and ensuring the construction progress.