中文摘要：

白鹤滩水电站地下洞室群规模宏大,厂房区构造应力高,地质条件复杂。主厂房第I层施工期,围岩变形和稳定问题突出。根据主厂房第I层开挖支护完毕后围岩变形监测资料,结合地质资料、施工情况,分析主厂房围岩变形规律与机制。统计分析得到,在高地应力和软弱地质构造控制下,围岩位移量值较大;由于右岸场区初始地应力大于左岸,右厂扩挖跨度大于左厂,且不良地质构造较左厂发育,右岸主厂房围岩变形量值普遍大于左厂;受初始最大主应力方向影响,左右岸主厂房拱顶和下游拱肩围岩变形普遍大于上游拱肩,且围岩变形较大部位均发育软弱构造带或岩体较破碎;围岩位移与开挖卸荷关系密切,监测断面附近开挖时,位移–时程曲线随开挖呈台阶式增长;岩体质量较好的洞段,掌子面的位移空间效应范围约一倍洞室跨度;软弱构造处,围岩变形在较长时期内随施工活动小幅跳跃增长,掌子面空间效应达到两倍洞室跨度;围岩时效变形不明显;软弱构造处围岩变形速率数倍于完整岩体。分析总结白鹤滩水电站地下厂房围岩变形规律对保障施工期安全和预测下阶段开挖围岩稳定性具有重要意义。

英文摘要：

The underground powerhouse cavern group in Baihetan hydropower station is in an extremely grand scale. Geostress in powerhouse area is relatively high and geological condition is quite complicated. The problems of surrounding rock deformation and stability are serious during the first layer of main power houses construction.. Based on deformation monitoring data after excavation of I layer,the deformation characteristic of the surrounding rock in main power houses are systematically analyzed,combining geological conditions and construction information. The mechanism of deformation characteristic is illustrated as well. Analysis shows that under the control of high ground stress and weak tectonic zone,surrounding rock deformation is relatively large after the I layer excavation in both riversides;Resulting from the larger ground stress in right bank than that in left bank,the larger expanding excavation span in right bank and more pervasive adverse geological structures development in right site area,surrounding rock deformation of main house in right bank is thus generally larger than that in left bank; Deformation in vault and downstream spandrel is generally larger than that in upstream due to the maximum principle stress direction;It is observed that there are usually weak tectonic zones or poor quality rock mass where the deformation is more pronounced;Surrounding rock deforms closely related to excavation. The deformation-time curves exhibit step-increase when excavates near the monitoring section. As for the tunnel section where rock mass quality is relatively good,the span of spatial effect is about the cavern span. However,for the tunnel section with weak tectonic zones,deformation keeps continuous increment following construction. Distance of spatial effect reaches approximately two diameters of cavern span. Rock mass deformation exhibits time-independent;Deformation velocity near tectonic zone is usually several times of that at quite good quality rock. To analyze and summarize the surrounding rock defo