Mechanism of Reservoir Water in the Deformation of Hefeng Landslide

The trial impoundment was carried on in Three Gorges Reservoir from September 27, 2008. There were strong deformation and failure in Hefeng (鹤峰) landslide when the reservoir water level descended from the altitude of 173 m. It indicates that the deformation is closely related to reser-voir water fluctuation. For this reason, the effect of reservoir water in the deformation was studied, taking Hefeng landslide as an example in this article. First, the geological characteristics and deforma-tion situation of strong deformation region are analyzed to disclose the intrinsic factors and the pattern of the deformation under the condition of water level fluctuation. Second, the stabilities of the landslide are calculated during the rising and descending processes, and the corresponding relationship between reservoir water level fluctuation and landslide deformation is further identified. At last, the seepage fields and the force condition of landslide body below the phreatic line are analyzed to reveal the effect of reservoir water. Moreover, it can be concluded that for better permeable reservoir landslide, during reservoir water rising, the favorable effect of seepage force weakens the unfavorable effect of uplift force, so the rising of reservoir water has little effect on the stability, and no deformation is caused; but during the descending of reservoir water, the unfavorable effect of seepage force is superimposed on the unfavorable effect of the uplift force, which causes the stability to dramatically decrease and leads to the failure of the accumulation body in front of the landslide.