双江口水电站地下厂房顶拱开挖围岩损伤分析及变形预警研究

Damage analysis and deformation early warning of surrounding rock mass during top arch excavation of underground powerhouse of Shuangjiangkou hydropower station

以双江口水电站左岸地下厂房为研究对象,构建三维空间"体"微震监测系统,对顶拱开挖过程围岩微震信号进行实时拾取,依据微震活动特征圈定围岩损伤区域,结合常规监测结果与现场探勘情况分析微震活动时空演化与施工动态响应关系;引入分形–岩石力学理论,揭示围岩渐进损伤直至宏观变形全过程分形维值演化规律。研究结果表明:微震活动与施工工况、地质条件密切相关,安装间段厂横0-57m^0-43m下游侧拱肩微震事件聚集由爆破开挖强度及长大岩体裂隙控制;围岩损伤表现出非剪切破裂特征,破裂尺度增大时微震信号呈现低频特征;分形维值出现陡降是岩体发生宏观变形的前兆信号。研究结果可为类似地下厂房开挖围岩损伤分析及变形预警提供参考。

A three-dimensional spatial microseismic monitoring system of the underground powerhouse at the left bank of Shuangjiangkou hydropower station was constructed to pick up the surrounding rock microseismic signals during the excavation period, and the surrounding rock damage area was determined according to the microseismic activity characteristics. The relationship between spatio-temporal evolution characteristics and construction dynamic response of microseismic activity was analyzed based on conventional monitoring results and on-site exploration,and the evolution law of the fractal dimension of the surrounding rock from progressive damage to macroscopical deformation was revealed adopting the fractal-rock mechanics theory. The results show that the microseismic activity is closely related to the construction conditions and geological conditions. The microseismic event of the downstream side of 0–57 m–0–43 m in the installation interval is controlled by the blasting excavation strength and the giant rock mass fissure. The damage of surrounding rock mass exhibits non-shear rupture characteristics,and the microseismic signal shows low-frequency characteristics when the rupture scale increases. It is also revealed that the steep drop of the fractal dimension is the precursor signal of macroscopical deformation of surrounding rock mass. The research results can provide reference for the analysis of surrounding rock damage and deformation warning in underground powerhouse excavation.