岩体微震能量演化规律及渗透系数评估

Microseismic energy evolution law of rock and permeability assessment

基于大岗山水电站右岸边坡开挖过程中的微震监测数据,分析卸荷引起微震能量释放的时空规律,研究渗透系数增量的空间分布。结果表明：微震能量逐月累积等值线空间分布图可初步定量地识别和圈定边坡深部岩体损伤的区域及程度,微震能量沿软弱结构面易形成积聚带,并遵循能量的累积、释放和转移的规律。岩体因损伤而释放的微震能量与岩体渗透系数变化的趋势具有一致性。两卸荷裂隙带和断层外侧附近渗透系数改变量约为0.03-0.05 cm/s,而两卸荷裂隙带和断层之间的岩体的渗透系数约为0.04-0.097 cm/s。渗透系数的改变在软弱结构面交界处附近最为显著,表明在卸荷条件下,岩体的渗透特性受结构面的影响极大。利用开挖过程中岩体释放的微震能量,并结合开挖前边坡不同岩体的渗透系数,可对开挖后岩体的渗透系数进行评估。

Based on the microseismic results from Dagangshan righ-bank slope excavation,the evolution of released microseismic energy is studied. It is shown that the spatial distribution of month contour of microseismic energy accumulation can quantitatively identify and delineate the damage degree and region of deep slope. Microsesmic energy is easy to form an accumulation zone along weak structural surfaces,and follows the accumulation,release and transfer rules of energy. The released microseismic energy due to rock damage is consistent with the change trend of rock permeability. The permeability change for the two intensive unloading fissure stripes and fault lateral is about 0. 03 - 0. 05 cm / s,and about 0. 04 - 0. 097 cm / s for the two intensive unloading fissure stripes and fault fall,and the permeability changes most significantly in the vicinity of the junction of weak structural planes,indicating that,under excavation unloading conditions,both mechanical properties and permeability characteristics of rock mass are greatly influenced by the structure.According to the released microseismic energy and the different permeability coefficients of slope before excavation,the permeability coefferents of the slope after excavation can be assessed.