This paper presents an in-depth analysis of the deformation characteristics and reactivation mechanisms of a giant ancient translational landslide in the Three Gorges Reservoir (TGR) based on more than 6 years of monitoring data with the assistance of in situ surveys. The Outang landslide, divided into three active parts, has a total volume of approximately 90 million m³ and slides along weak interlayers (WIs). Since the impoundment, the landslide has been experiencing persistent deformations with some distinct movement signs. The temporal displacements are marked by seasonal cycles of fast displacements in the summer followed by almost imperceptible movements for the remainder of each hydrologic year. The spatial displacement rates gradually increased with the increase in altitude. The primary triggering factors for slope movement could transition from the drawdown of the reservoir water to the periodic rainfall. The affected areas by the former and latter are mainly concentrated in the front part and the upper part of the slope, respectively. The landslide exhibited a composite push-retrogression-type failure evolution with the fluctuating reservoir levels destabilizing rock masses at the front part of the landslide and the precipitation mainly mobilizing materials in the upper part of the slope. Currently, the landslide is in a state of continuous movement. The toe area and upper part of the landslide should receive high priority for the development of preventative measures.

本文基于6年以上的实地调查资料，对三峡水库（TGR）的一个古老的平移滑坡的变形特征和活化机制进行了深入分析。分为三个活动部分的Outang滑坡总体积约为9000万m ³并沿着薄弱的中间层（WI）滑动。自蓄水以来，滑坡一直持续变形，并带有一些明显的运动迹象。时间上的位移以夏季的快速位移的季节性周期为标志，随后在每个水文年的剩余时间内几乎看不到运动。随着海拔的升高，空间位移率逐渐增加。斜坡运动的主要触发因素可能是从水库水位下降到周期性降雨。前者和后者的影响区域主要集中在斜坡的前部和上部。滑坡表现出复合的推-退-型破坏演化，储层水平的波动破坏了滑坡前部的岩体的稳定性，而降水主要使斜坡上部的物质活动。当前，滑坡处于连续运动的状态。脚趾区域和滑坡的上部应优先制定预防措施。