Landslide disaster mitigation in the Three Gorges Reservoir, China

Abstract

The Xintan landslide, a fast-moving landslide that occurred on June 12, 1985, is located on the north bank of the Yangtze River at Xintan Town, Zigui County, Hubei Province, China. Investigations showed that this landslide travelled at a speed of about 20 m/s and induced a huge water wave with wave run-up of 54 m on the opposite shore. Back-analysis of water waves generated by the Xintan landslide is used to determine the friction angle of the sliding zone in a state of movement. Newton’s second law and the basic principles of kinematics are used to obtain landslide velocity by the method of back-analysis, and the volume conversion law and the viscous force formula in flow fields are applied to calculate the initial height of the water wave. In terms of continuity equation, movement equation of transient flow and water head loss theory in open channels in hydrodynamics, the propagation process of the landslide surge is divided into two stages: the sharp-decay stage and the slow-decay stage. It is assumed that the sharp-decay stage is a kind of exponen- tial decay and the slow-decay stage is a kind of water head loss with propagation distance in an open channel. Wave run-up on the opposite shore is calculated with the consideration of slope angle and run-up azimuth. It is concluded that an appro- priate value of the reduction factor of friction angle of the sliding zone is between 0.8 and 0.9, and the results have significance for the selection of the friction angle of the sliding zone in a state of movement and calculation of landslide velocity.