Abstract: The deep-seated reservoir ancient landslide often shows intermittent reactivation which corresponds to seasonal rainfall and periodic reservoir water level fluctuation. In this kind of reactivation, sliding and sliding dormancy occur alternately. This means that the sliding zone soils may experience shearing at different shear rates and consolidation with different durations. The kinetic equations are established based on three aspects, i.e., shear rate effect of residual shear strength in sliding, peak shear strength recovery in sliding dormancy and the initiation of sliding from sliding dormancy caused by pore-water pressure. Ring shear tests are performed on the soil samples from slip surface of Tangjiaocun-1 landslide in this paper. The results show that the residual shear strength is negatively dependent on the small range of shear rates and there is no decrease of residual shear strength after a larger shear rate even with a trend of small increase; the peak shear strength can be recovered within a short consolidation duration after the shearing ceased whereas the strength recovery is lost after a small shear displacement; and shear failure triggered by pore-water pressure lags behind the increase of pore-water pressure applied on sample, the lag implies pore-water pressure diffusion. The kinematic mechanism is then discussed based on the results of ring shear tests and the kinetic equations established above. These results may provide help for the prediction of deep-seated reservoir ancient landslides due to rainfall and/or reservoir water level fluctuation.

Key words: deep-seated reservoir ancient landslide, intermittent reactivation, shear rate effect, strength recovery, pore-water pressure diffusion