高应力地下厂房顶拱开挖过程围岩力学响应与稳定性分析

Mechanical response and stability analysis of surrounding rock mass during roof arch excavation of underground powerhouse under high in-situ stress

水电站地下厂房洞室群地质结构复杂、地应力高,施工期间围岩变形破坏现象频繁发生。针对某水电站高应力地下厂房开挖卸荷诱发顶拱破坏的问题,开展围岩损伤演化过程分析。利用微震监测技术实时记录地下厂房开挖期间围岩微破裂萌生、发育及扩展过程。结合常规监测、现场踏勘,揭示深部围岩损伤与施工动态的响应规律。采用数值模拟重现开挖过程应力场与位移场的渐进演化特征。研究结果表明:微震活动与施工状态、地质条件密切相关,厂房K0–40~K0–60区域微震事件聚集由强卸荷及节理、裂隙共同控制。开挖卸荷形成的高边墙水平应力及顶拱垂直应力加剧了围岩损伤沿开挖轴向扩展演化。震源参数在围岩变形破坏前表现为矩震级增大、视应力下降、累计视体积不变。研究成果可为类似地下工程开挖围岩损伤及稳定性评价提供借鉴。

The geological structure of underground powerhouse caverns of hydropower stations is complex and the ground stress is high.Deformation and failure of surrounding rock mass occur frequently during construction.In order to solve the failure of roof arch during excavation of high stress underground powerhouse of one power station,the damage evolution process of surrounding rock was analyzed.The microseismic(MS)monitoring technology was used to record the process of surrounding rock mass microfracture initiation and propagation during excavation of underground powerhouse in real time.The response laws of deep surrounding rock damage and construction dynamics were revealed through routine monitoring and site survey.The progressive evolution characteristics of stress field and displacement field during excavation were reproduced by numerical simulation.The research results show that the MS activity is closely related to the construction state and geological conditions.The MS events gathering in the K0-40-K0-60 area of the powerhouse are jointly controlled by strong unloading and joint fissures.The horizontal stress of the high side wall and the vertical stress of the top arch aggravate the damage evolution along the excavation axis.The focal parameters show that the moment magnitude increases,the apparent stress decreases,and the cumulative apparent volume remains unchanged before the deformation and failure of the surrounding rock mass.The research results can provide reference for the damage and stability evaluation of surrounding rock mass during excavation of similar underground engineering.