岩质边坡微震活动特征及其施工响应分析

岩石高边坡稳定性是水电工程建设能否顺利进行的关键问题之一。锦屏一级水电站左岸边坡地应力高,断层裂隙发育,岩体卸荷深度大,地质条件复杂,边坡在施工期和运行期的稳定性问题十分突出。介绍左岸边坡微震活动特征,并对开挖卸荷过程微震活动性时空分布规律以及与不同时段、区域的施工工况进行对比分析,对岩石微破裂萌生、发育、扩展、聚集趋势与岩体损伤关系进行探讨,得到左岸边坡微震活动与施工响应之间的相互关系。结果表明:大坝基坑、煌斑岩脉置换斜井、1 670 m雾化区边坡排水廊道开挖和边坡弱层固结灌浆引起的深部岩体卸荷松弛而诱致微震活动性,可以很好地揭示和反映现场施工工况。研究成果可供其他类似岩质高边坡工程借鉴、参考。

ANALYSIS ON CHARACTERISTICS OF MICROSEISMIC ACTIVITY AND ITS RESPONSE TO CONSTRUCTION AT ROCK SLOPE

The stability of high rock slope is one of the important issues during the construction of hydropower station. The stability of the left bank slope at Jinping I hydropower station was the key issue due to its high geo-stress，developed faults and fissures，large-scale excavation，deep unloading and complicated geological conditions. The characteristics of the microseismic activity of the left bank slope were introduced firstly. Analyses of the temporal and spatial distributions of the microseismic activity in the processes of excavation-induced unloading and under the excavation conditions during the different periods and in the different regions were conducted. The correlation among the initiation，propagation，extension and coalescence of micro-fractures of rock and the rock mass damage were discussed. The correlation between the microseismic activity and the construction response at the left bank slope was also obtained. The results showed that the microseismic activity induced by the unloading relaxation of the deep rock mass as results of the excavation of the foundation pit of dam，the X shafts for lamprophyre vein replacement and the drainage tunnels at the elevation of 1670 m and the consolidation grouting of weak layers inside the rock slope reflected in real time the construction conditions on site very well.