瀑布沟电站地下厂房洞室群施工期监测分析

Monitoring Analysis of the Underground Cavities in Pubugou Hydropower Station during the Construction Period

瀑布沟水电站地下厂房洞室群包括6条引水隧洞、地下厂房、主变室、尾调室和2条尾水隧洞,布置于大渡河左岸花岗岩山体中。本文在简介洞室群布置、工程地质条件、监测设计和实施情况的基础上,着重分析了地下厂房、主变室和尾调室等三大洞室的变形量级与变形特征,评价了洞室群的稳定性。瀑布沟水电站地下厂房洞室群围岩质量整体较好,变形一般小于40 mm,但是局部受结构面影响变形较大,最大变形可达105 mm。变形较大部位一般出现在侧墙的上部,如主厂房的岩锚梁部位附近。结构面对围岩变形的控制作用显著,其上下盘的差异变形导致了施工过程中的岩锚梁开裂现象。因此,洞室群监测设计和岩锚梁结构设计均需要考虑这类局部差异变形现象。围岩变形的时效特征不显著,开挖施工结束后围岩变形与支护结构应力收敛速度较快,位移变化速率基本在1 mm/月以内,应力变化速率基本在5MPa/月以内,洞室群稳定状况良好。

Underground cavities of Pubugou Hydropower Station,including six diversion tunnels,underground powerhouse,the main transformer room,the tailwater room and two tail-water tunnels,were arranged on the right bank of the Dadu River in the granite mountain.This paper,based on caverns layout,engineering geological conditions,monitoring design and implementation,focused on analysis of cavern deformation and distribution characteristics of the underground plant,the main transformer room and the tailwater room,and evaluated stability of the cavern group.Pubugou rock caverns＇ overall quality is better,so the deformation of the surrounding rock is smaller during the construction process and is generally less than 40mm,but due to structural surface effect the maximum deformation is up to 105 mm;The parts of rock with large deformation mainly found in the upper side wall,such as the main plant site near by.The structure plays main role in controlling rock deformation,so differences between its upper and lower plate deformation led to cracking in the rock-anchored beam during construction process.Therefore,monitor design of the chamber group and rock-anchored beam structure design would require consideration of these local variations in deformation behavior.Limitation of surrounding rock deformation characteristics are not significant.As excavation was over,the rock deformation and stress convergence speed become stable,the displacement changes with basic rate of 1mm / month or less,the basic rate of stress change is 5MPa / month or less,the cavity is in good condition.