锦屏I级水电站地下厂房施工期围岩变形开裂特征及地质力学机制研究

 锦屏I级水电站是雅砻江流域最为重要的控制性梯级电站。地下电站的规模巨大并且赋存的地质环境条件十分复杂，特别是岩石的相对低强度和高地应力特征，地下电站在施工过程中遇到前所未有的有关围岩稳定及支护设计方面的难题。结合地质、监测、物探、施工及试验资料，分析地下厂房洞室群围岩及支护结构的变形开裂及破坏失效的特征。探讨地下电站区的地应力状态、岩体结构、岩石的加卸载力学特性等对围岩变形开裂的影响规律，解释围岩变形破坏的地质力学机制。高地应力及其方向使得主厂房和主变室下游侧围岩(特别是拱腰)的切向应力加载效应明显，易于压致劈裂，而上游侧边墙等法向应力卸荷强度较大，易于卸荷拉裂松弛。高应力条件下破裂围岩具有一定的流变特性，表现出由表及深的渐进性特征，反映随围岩松弛而发生的破裂岩体的时效变形。主厂房和主变室上游侧为缓倾角顺向坡而下游侧为反向坡，在二次应力场作用下下游侧易弯曲折断而上游侧很难剪切滑移。厂房区大理岩具有相对低强度高脆性力学特性且具有较低的应变强度特征，卸荷条件下易于压致拉裂。

GEOMECHANICS MECHANISM AND CHARACTERISTICS OF SURROUNDING ROCK MASS DEFORMATION FAILURE IN CONSTRUCTION PHASE FOR UNDERGROUND POWERHOUSE OF JINPING I HYDROPOWER STATION

Jinping I Hydropower Station located in the Southwest China is a key cascade and control underground hydropower project at the Yalong River. The project is very huge and the underground powerhouse system is very complicated，as well as the complex geological conditions，lower strength for rock relative to very high geostress especially. The challenge which no found in historical projects is presented by two dominate aspects in the construction. The two ones are stability and reinforce of surrounding rock. The characteristics of deformation split of surrounding rock and failure of supporting structure is described based on the geological conditions，monitor and geophysical prospecting，investigations in-situ and tests data. The correlations are discussed which deformation failure of surrounding rock and supporting structure with geostress，rock mass structure and mechanical property of rock under loading and unloading. The geomechanics mechanism of deformation failure of the surrounding rock and supporting structure is explained. The tangential loading stress is rather large and inclined to split pressed at downstream side(especially hance) of main powerhouse and main transformer house，but the normal unloading stress is rather larger and inclined to tension and relaxation unloaded because of the high geostress and its direction. The rheological behaviour of the fracture surrounding rock is presented，and is gradually charactered from surface to deep，the time-dependent deformation of fracture rock mass with surrounding rock relaxation is showed. The surrounding rock at downstream side is easy to bend and break-off and low susceptibility to shear and slide of main powerhouse and main transformer house under secondary stress field，because that the upstream side is bedding but the downstream inverse slope with low dip angles. The powerhouse marble is presented that relative lower strength，heavy brittle and lower strain strength，easy to tension pressed under unloading.