锦屏一级水电站地下厂房围岩开裂变形机制研究

针对锦屏一级水电站地下厂房高应力、低强度应力比条件下开挖施工引起的围岩变形开裂及相关力学问题,从全空间赤平投影解析、平面投影应力特征等多角度全方位研究地下厂房区地应力场分布特征及规律;并结合力学定性分析和三维数值模拟等手段对地下洞室群围岩变形开裂机制进行深入分析,研究洞室群围岩开挖损伤演化规律。研究表明,锦屏一级地下厂房区域出现的围岩、喷层较大变形乃至破坏现象本质上是由高地应力和相对较低的岩体强度形成的不利组合所造成的,在主厂房、主变室的拱腰、拱座和边墙以及母线洞侧墙等部位出现的开裂破坏,属于典型的高应力、低强度应力比条件下围岩的卸荷变形与破坏。提出锦屏地下厂房围岩变形开裂概化模型,为地应力场反演和施工过程的数值仿真分析提供重要参考和定性依据;最后针对开挖维护围岩稳定性问题提出相应的建议,为锦屏一级地下厂房的开挖施工及动态支护设计提供技术支持。

STUDY OF DEFORMATION AND CRACKING MECHANISM OF SURROUNDING ROCK OF JINPING I UNDERGROUND POWERHOUSE

Aiming at the deformation and cracking phenomena of surrounding rock mass during the excavation of Jinping I hydropower station underground powerhouse under the conditions of high stress and low strength stress ratio，the characteristics and laws of in-situ stress field are studied entirely by the stereographic projection method and projection stress on typical planes. The deformation and cracking mechanism of surrounding rock of underground caverns group are deeply analyzed through mechanical qualitative analysis and 3D numerical simulation；and the damage evolution law of surrounding rock is studied. The results show that the relatively large deformation and cracking phenomena of surrounding rock and shotcrete layer of underground powerhouse are caused essentially by the adverse combination of the high ground stress and relatively low rock strength. The cracking failures in haunch，arch abutment and side wall of main powerhouse and main transformer chamber，and in side wall of busbar tunnels are typical unloading deformations and failures under the conditions of high stress，low strength stress ratio. The generalized model of surrounding rock deformation and cracking of underground powerhouse is presented. It affords important reference and qualitative basis for the back analysis of in-situ stress field and the numerical simulation of excavation process. Finally，some advices are given to maintain the stability of surrounding rock mass. All the results afford technical support to the construction and dynamic support design of the underground powerhouse.