岷江某水电站库区1#滑坡复活机制分析

岷江某水电站库区1^＃滑坡,系白水寨古地滑堆积体下部,受1933年叠溪地震影响,而形成的一个老滑坡。2001年水库正常蓄水(1475m)后,滑坡出现明显变形迹象,2003年初,库水位下调至1470m,滑坡变形开始趋缓。笔者根据滑坡区地形地质条件,结合现场调查访问、监测资料分析,认为水库蓄水所引起的孔压(浮托力)增加是古滑坡复活的主要动因。二维FLAC数值模拟表明,在库水位由1450m(蓄水前)→1475m→1470m的变动过程中,滑坡变形呈现出相对平稳→急剧增加→增速减缓的特征,证实了上述认识。稳定性计算表明,在蓄水1475及暴雨或地震条件下,滑坡稳定性系数为0.90~0.99,即该滑坡将失稳。为使水库恢复至正常蓄水位,对该滑坡进行治理非常必要,治理方案建议以抗滑支挡为主,排水措施为辅。

ANALYSIS OF REVIVIFICATION MECHANISM FOR A LANDSLIDE ON A HYDROPOWER STATION RESERVOIR IN MINJIANG

The landslide examined in this paper is located in a hydropower station reservoir in Mingjiang River. It is 0.5 km away from dam foundation. The bottom of Baishuizhai older landslide deposit was affected by Diexi Earthquake in 1933 and formed an old landslide (i.e., the examined landslide). The landslide had great deformation after water storage in 2001 at the normal level of 1475 m above sea level. Early in 2003, the water level of reservoir declined to 1470 m and the deformation had slowed down. The terrain and geology conditions were examined and combined with field investigation and analysis of the monitoring data. The increase of core pressure caused by water storage was considered as the major reason of the recovery of this old landslide. A 2D FLAC numerical modeling showed that when the water level changed from 1450m(before water storage)to 1475 m and then to 1470 m, the deformation of landslide had changes of relative smooth to increase dramatically, then to increase slowly down, respectively. Calculation of stability showed that, in the condition of 1475 m water level or earthquake, the coefficient of landslide stability is 0.9~0.99. It means the landslide would occur. In order to make the water level to normal, the landslide needs some remedial measures . The sliding-block with drainage is suggested to be the main method.