白鹤滩水电站岩质边坡微震活动特征研究*

白鹤滩水电站左岸边坡高陡,应力条件复杂,存在LS_(331)、LS_(337)、LS_(3319)层内错动带,F17断层等软弱结构面,施工期和运营期安全问题十分突出。为评价其左岸边坡开挖稳定性,利用微震监测系统对边坡微震活动进行实时监测,并分析微震活动的时空以及震级分布,揭示岩质边坡开挖扰动下的微震活动特性及其施工响应特征。结果表明:开挖强度越大,边坡损伤越大,微震活动越活跃;爆破后0.5h内应力急剧调整,微震活动频繁;震级分布在-1.6~0.4之间,爆破开挖诱发大量震级小能量低的微震事件,诱发边坡的渐进损伤;软弱结构面是微震事件的主要活动区域,具有发生破坏变形的可能性;左岸边坡岩石破裂以复合型破坏和剪切破坏为主,伴随少量拉伸破坏。该研究可为工程后续开挖和支护提供参考,为同类微震活动特性分析提供一定的借鉴。

Micro-seismicity Analysis of the Left Bank Rock Slope at Baihetan Hydropower Station

The stability of the left bank slope at Baihetan Hydropower Station is remarkable due to its cracks and fault such as LS₃₃₁, LS₃₃₇, LS₃₃₁₉ and F₁₇, which result in complex stress.A micro-seismic monitoring system was established to monitor and analyze the micro-seismicity to evaluate the stability of the left bank. Through analyzing the spatio-temporal and micro-seismic magnitude distribution of micro-seismic activities, the characteristics of micro-seismicity and response of construction were revealed. The result shows that: the fiercer the excavation was, the more damage to the slope was caused, and the more active the micro-seismicity is; the stress adjusted drastically and the micro-seismic activities was within half an hourafter blasting; the blasting excavation induces numerous micro-seismic event, which is small magnitude and with a little energy, causes damage to slope step by step; the micro-seismic events mainly spread in the weak structures planes which shows that the weak structure are the dangerous areas; most rock failures are in form of compound fracture and shear fracture. This research providessignificant references for later excavation and supports to Baihetan left bankslope, and better understandings will be obtained for other characteristics of micro-seismic activity.