锦屏一级水电站左岸坝肩边坡施工期稳定分析

锦屏一级水电站左岸坝肩高陡边坡地质条件复杂、主要发育有f5、f8、f42-9断层，煌斑岩脉X，顺坡卸荷裂隙及深部裂缝等结构面，其中断层f42-9、煌斑岩脉X和深部裂缝SL44-1组合形成的左岸坝头拉裂变形体，在边坡施工期的稳定性问题突出，特别是当边坡开挖至1 780 m高程时拉裂变形体前沿剪出口阻滑岩体被完全挖除，f42-9断层在开挖坡面出露，拉裂变形体稳定条件恶化，稳定性急剧下降。采用考虑开挖过程的有限元强度折减法分析开挖边坡在施工期的稳定性，并提出了一种新的边坡失稳判据：通过滑体内关键部位测点水平位移随折减系数的变化率，即水平位移增量与强度折减系数增量之比值 和强度折减系数 关系曲线的突变点来确定边坡的临界失稳状态。通过与其他边坡失稳判据相比较，验证了该判据的合理性和实用性，同时基于该判据计算了边坡开挖加固至不同高程下的稳定安全系数，合理评价左坝肩边坡施工期的整体稳定与安全性。

Stability analysis of abutment slope at left bank of Jinping-I Hydropower Project during construction

The geological conditions of the high and steep abutment slope at left bank of Jinping-I Hydropower Project are very complicated,mainly developed with the faults of f5,f8,f42-9,the lamprophyre veins of X,the release fractures oriented parallel to slope surface and deep fractures.The combination of the fault of f42-9,the lamprophyre veins of X and the deep fracture of SL44-1 form a tensile dehiscent deformable body at the abutment slope of the left bank;the stability of the abutment slope is very bad during construction,especially when the slope is excavated to the elevation of 1 780 m,all rock masses that prevent the tensile dehiscent deformable body from sliding are excavated;the outcrop of the fault of f42-9 at the surface of the excavated slope makes the stability of the tensile dehiscent deformable body abruptly become worse.The strength reduction FEM considering excavation process is applied to calculate the stability safety factor of the abutment slope;and a new slope instability criterion is proposed as follows: in finding the mutant site on the relationship curves between of key points and the strength reduction factors,the critical state of instability of the slope could be determined;in this criteria,,which stands the change rate of horizontal displacement with the strength reduction factors,is the ratio of the horizontal displacement’s increment and the strength reduction factor’s increment.Comparing with other slope instability criteria,a new criterion is proved to be a reasonable and practical slope instability criterion;based on this criterion,the stability safety factors are calculated when the slope is excavated and reinforced to different elevations;the overall stability and security of the abutment slope at the left bank are reasonably evaluated during its construction.