Abstract: The underground powerhouse of large-scale hydropower station is large, and the relaxation zone will be formed in surrounding rock due to structural relaxation and stress relaxation in the process of blasting excavation. Generally, the sound wave detection and borehole TV method are used to monitor the relaxation depth and change trend of surrounding rock, which provides basic data for optimization of excavation of underground powerhouse cavern and for analysis and research of surrounding rock stability. With the continuous excavation of underground powerhouse, the distance between the top arch and the excavation base is getting further and further, so it is difficult to detect the relaxation of surrounding rock at the top of the powerhouse at the base, which often leads to data lack in the middle and later stages of excavation. In this paper, the relaxation depth of surrounding rock at the top of underground powerhouse of a large hydropower station is detected from the observation well in the anchorage holes above the underground powerhouse, which provides a new idea for monitoring of the relaxation depth of surrounding rock and offers reference for other similar projects.

Key words: underground powerhouse, single-hole sonic, borehole television, relaxation of surrounding , rock

摘要： 大型水电站地下厂房规模宏大，爆破开挖过程中因结构松弛和应力松弛，将形成围岩松弛圈，一般采用声波检测和钻孔电视方法检测围岩松弛深度及变化趋势，为地下厂房洞室开挖施工优化和围岩稳定性分析研究提供基础资料。随着地下厂房不断下卧开挖，厂房顶拱距离开挖基面越来越远，在开挖基面很难实施厂顶围岩的松弛检测，往往导致地下厂房开挖中、后期的厂顶围岩松弛检测数据缺失，进而影响地下厂房围岩松弛深度资料的完整性。笔者介绍了在某大型水电站地下厂房上方锚固洞的底板观测孔内检测厂顶围岩松弛深度，为地下厂房顶拱围岩松弛深度检测提供新思路，对其他类似工程具有一定的借鉴作用。

关键词: 地下厂房, 单孔声波, 钻孔电视, 围岩松弛