基于改进刚体弹簧方法的开挖损伤演化分析

NUMERICAL SIMULATION OF EXCAVATION DAMAGED ZONE USING THE MODIFIED RIGID BODY SPRING METHOD

基于改进刚体弹簧方法研究结构面在围岩开挖过程中的响应及围岩损伤区范围。改进刚体弹簧方法基于Voronoi网格,能够显式模拟细观裂隙的起裂、扩展和贯通过程。界面破坏准则结合了Hoek-Brown准则和抗拉强度准则,能同时考虑拉裂和剪切2种破坏模式。计算采用渐变式的网格,对重点关注区域进行网格局部加密,这种方式可以精细考虑开挖面附近的围岩损伤同时提高计算效率。为验证模型的合理性,在弹性条件下对一个简单算例进行计算,计算结果与有限元结果吻合良好。以锦屏二级水电站引水隧洞为例,计算NWW向优势陡倾节理在不同开挖步对围岩损伤区的影响,损伤区分布规律与现场观测结果基本吻合。

This paper describes the numerical modeling of excavation damaged zone(EDZ) in surrounding rocks with embedded structural planes. A modified rigid body spring method(RBSM) was proposed to simulate the initiation and propagation of micro cracks. Both the tensile and shear failures were considered by introducing a failure criterion which combines the Hoek-Brown criterion and the tensile strength criterion. The rock material was represented by an equivalent discrete assembly of rigid blocks based on a degradation Voronoi mesh. A simple case was employed to demonstrate the validity of the proposed model,and the simulation results were compared with ones from the finite element method. At last,the EDZ of the diversion tunnel in the Jinping II hydropower project was studied using the proposed model with the emphasis on the NWW joint and some suggestions were given on the reinforcement project. The simulated EDZs were generally in agreement with the in-situ observation.