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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。
The underground caverns at Baihetan Hydropower Station are large in scale with high tectonic stress and complicated geological conditions in the plant area. During the construction of the first floor of the main building, the deformation and stability of surrounding rock are outstanding. According to the deformation monitoring data of the surrounding rock after the excavation and support of the first floor of the main building, the deformation laws and mechanisms of the surrounding rock of the main building are analyzed based on the geological data and construction conditions. The statistical analysis shows that under the control of high ground stress and weak geological structure, the displacement of surrounding rock is relatively large. Because the initial stress in the right bank field is larger than that of the left bank, the expansion span of the right plant is larger than that of the left one and the unfavorable geological structure is more developed than the left one. The deformation of surrounding rock of the right bank main plant is generally larger than that of the left factory. Due to the influence of the initial maximum principal stress, the deformation of the surrounding rock of vault and downstream arch of the left and right bank buildings is generally larger than that of the upstream spandrel and the deformation of the surrounding rock is weak The tectonic belt or rock mass is more broken; the displacement of surrounding rock is closely related to the excavation and unloading; when the excavation is near the cross section, the displacement-time curve increases stepwise with the excavation; the rock mass has good quality, The displacement effect of surface is about one time the span of cavern; in the weak structure, the deformation of surrounding rock increases slightly with the construction activity in a long period of time, and the space effect of the carapace surface reaches twice the cavern span; the deformation of surrounding rock is not obvious The deformation rate of surrounding rock in weak structure is several times that of intact rock mass. It is of great significance to analyze the deformation of the surrounding rock of the underground powerhouse of Baihetan Hydropower Station to ensure the safety during construction and to predict the stability of surrounding rock during excavation in the next stage.