某水电站现场监测资料表明，电站导流洞出口边坡开挖后有不间断变形，而且速率较大。为查明出口边坡潜在变形破坏范围及特征，对监测资料进行分析，同时采用极限平衡和三维数值模拟手段，对边坡稳定状态进行评价。结果表明：开挖前边坡能够自稳，开挖后如不及时支护，表层第四系土层会发生向开挖面的滑移；侧面边坡变形具有时效性，随时间推移变形破坏范围会向上部逐渐扩展。建议通过补充钻探和物探等措施，详细查明第四系覆盖层分布范围及厚度，同时通过现场试验等手段核实对边坡稳定状态极为敏感的第四系土层和强风化板岩层抗剪强度参数，在此基础上制定可靠的边坡支护措施。

In-situ monitoring data of a hydropower station located in southeast China revealed constant and rapid deformation in the slope at the diversion tunnel outlet. To find out the deformation scope and characteristics, the in-situ monitoring data was analyzed in detail, and in association with the limit equilibrium analysis and 3D numerical simulation, the slope stability was evaluated. Research results indicated that the slope was stable before excavation; but without effective support, soil layer in the quaternary system would slide toward the excavation face after excavation. Deformation of the side slope would develop with time, which means that the deformation scope would extend to the upper part gradually in the absence of in-time support. Suggestions were given as follows: before designing the slope support measures, firstly, more drilling or physical inspection work are needed to detect the scope and depth of quaternary soil layer; secondly, in-situ tests are needed to check the shear strength of the easily-slide quaternary soil and strongly weathered slate layers.