脆性裂隙围岩的损伤力学分析及现场监测研究

STUDY OF FIELD MONITORING AND DAMAGE MECHANICS ANALYSIS OF BRITTLE FRACTURED ROCK MASSES

我国西南地区许多水电站基岩为脆性围岩或位于高地应力区。其地下式厂房洞群边墙经常出现较深的开裂区。采用断裂和损伤力学模型结合现场监测工作来研究此现象。该模型可考虑多组节理中裂隙面的各种几何损伤参数。根据应变等效假设可得到基于莫尔-库仑准则的损伤本构方程。运用断裂力学原理分析岩体在开挖过程中原有裂隙产生次生裂纹的现象,推导出岩桥贯通的破坏准则和损伤演化方程并将前述的模型程序化。再运用该新的分析程序对一个水电站洞群工程进行稳定性分析。最后,运用该工程现场监测数据得到的围岩松弛开裂区深度与程序推算的结果做比较,说明二者的劈裂区发育规律很相近。

Many hydropower stations in Southwest China are located in regions with high geostresse or brittle rock masses.Deep fracture zones occur often in the sidewalls of the underground caverns.The theory and method of fracture and damage mechanics are adopted to study this phenomenon.This model can take into account area and orientation of fractured surfaces of multiple joint sets,as well as spacing and density of joints.Under the assumption of equivalent strain principle,a damage constitutive model is established based on Mohr-Coulomb criterion.The theory of fracture mechanics is applied to analyze the occurrence of secondary cracks during cavern excavation.The failure criterion for rock bridge coalescence and damage evolution equation are derived.A new subprogram for the above-mentioned damage constitutive model and damage evolution equation is developed.The program is then applied to stability analysis of an underground cavern group of a hydropower station.The results are compared with the depth of the relaxation and fracture zone in surrounding rock obtained from field monitoring.The distribution of splitting zone obtained from the proposed model is consistent with the field monitoring data.Therefore,the proposed model is validated.