为了研究中国西南地区双江口水电站高地应力地下厂房洞室群开挖卸荷围岩力学响应与稳定性,构建高精度微震监测系统,并采用离散元法开展数值模拟.分析了开挖卸荷引起的围岩时空损伤特征,研究了高地应力与结构面共同控制下围岩塌方形成过程微震震源参数演化规律.建立了地下厂房洞室群三维离散元数值模型,揭示了开挖卸荷引起的围岩变形特征.研究结果表明,高地应力地下厂房洞室群开挖卸荷引起的微震事件活动频繁,主厂房大桩号顶拱区域围岩损伤严重;在塌方发生前,微震事件数量和累积能量释放快速增长,视应力陡增之后出现下降,剪切以及混合型式的微破裂数量和占比显著增加;地下洞室最大位移基本位于拱肩区域.微震监测数据和数值模拟结果显示出较好的一致性,可为高地应力地下厂房洞室群围岩损伤评估和灾害预警提供重要参考.
To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation, a microseismic (MS) monitoring system was established and the discrete element method (DEM)-based numerical simulation was carried out. The tempo-spatial damage characteristics of rock mass were analyzed. The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated. Additionally, a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass. The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently. The large-stake crown of the main powerhouse was the main damage area. Prior to the rock collapse, the MS event count and accumulated energy release increased rapidly, while the apparent stress sharply increased and then decreased. The amount and proportion of shear and mixed MS events remarkably increased. The maximum displacement was generally located near the spandrel areas. The MS monitoring data and numerical simulation were in good agreement, which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.