大型地下硐室群施工期围岩应力变形及稳定分析

Stress deformation and stability analysis for surrounding rock mass during construction of large underground caverns

猴子岩水电站地下厂房硐室群工程地质条件复杂,岩体节理裂隙发育、受多条断层和挤压破碎带影响,加之布置于中-高地应力区域,施工过程中硐室围岩的变形和破坏较为明显,为确保工程施工安全,须对整个硐室群施工期的应力变形及稳定进行分析。结合相关设计参数和开挖支护实施方案,建立了猴子岩地下厂房硐室群的三维有限差分计算模型,并对其地应力场分布进行了反演,在此基础上对硐室群整个施工过程进行了全程模拟。计算结果表明:随着硐室开挖临空面的扩大,上下游边墙应力松弛现象较为明显,在断层出露带、机坑隔墙底部出现了不同程度的应力集中;开挖过程中围岩位移逐渐增大,在硐室连接处出现了大变形。设计支护方案实施后可以较好地限制围岩变形,减小塑性区面积,工程实践说明该方案较为合理。

Geological conditions of the underground openings of Houziyan hydropower station are complex,i. e.developing of jointed fractured rock mass,being influenced by multiple faults and compressive fracture zones,and being located in the area with middle-high initial stresses. The deformation and damage of the surrounding rock mass are obvious during construction. In order to ensure the safety of construction of works,it is necessary to analyze the stress deformation and stability of the whole opening group during the construction period. Based on the relevant design parameters and support schemes for excavation,a three-dimensional finite difference model is established for the underground openings of the Houziyan hydropower station, and the inversing stress field distribution and the entire construction process of openings are simulated. The analysis results show that with the expansion of free surface excavation,the stress relaxation of the upper and lower reaches of the side wall is more remarkable,and that the stress concentration of different degrees appears in the fault-exposed belt and at the bottom of the machine pit wall. The displacement of the surrounding rock during excavation is gradually increasing; and large deformation occurs at the connecting place of the openings. The supporting scheme can limit the deformation of the surrounding rock mass and reduce the area of the plastic zone,which means that the support scheme is reasonable for the construction of the openings.