Prediction of landslide surge in reservoir lies in the calculation of sliding velocity. For the present, the application of formula commonly used for predicting sliding velocity in projects has been limited within a certain range in that both the complicated influencing factors and controling conditions are simplified. Based on the principles of discrete element method for calculating the rock velocity, the sliding velocities of landslide masses in various zones at different moments are acquiried by means of the statistical analysis. Taking the deformation and failure mechanism of certain reservoir slope in the upstream of the Yellow River as research object, the dynamic change process of sliding velocity under the potential condition of instability is analyzed and predicted through the discrete element method and the analysis and prediction of the surge height are carried out according to the velocity of landslide masses while sliding into water.
Slope instability in reservoir is a kind of geological disasters, which emerges in the construction of hydropower projects. The surge caused by the process that landslide masses slide into water at very high speed threatens the sailing ships, the residents on both banks of the reservoir, and the security of hydraulic structures like barrages upstream and downstream. The large-scale surge brought about by huge high-speed landslides such as the Vaiont landslide in Italy in 1963, the reservoir landslide in Tuoxi of Hunan province in 1961 and the Xintan landslide of the Three Georges in 1985 caused serious casualties and property losses.
The calculation of the sliding velocity is the key to the evaluation of the disaster of slope landslides in reservoir and the predictive analysis of surge. The dynamic change features of the sliding velocity is crucial for understanding the dynamic mechanism in the developmental and change process of landslides and the influencing factors of sliding velocity. Such empirical formula methods as energy method, Scheidegger method and Pan Jiazheng method are usually adopted and taken as reasonal references for the predictive analysis of sliding velocity in projects. As the infuencing factors and control conditions are simplified to some extent in the formulae, the application of those methods are limited within a certain range and their estimation results tend to deviate far from the autual conditions. For instance, if the landslide mass is regarded as mass point, it is too simple to calculate the velocity by virtue of the overall gravity center of landslide mass; if the velocity is calculated by means of kinetic energy theorem, it is applicable to the linear sliding surface, but for non-linear sliding surface, the error is big. Besides, if the consideration is given to the average velocity of the whole sliding process, the dynamic change features in the sliding process of landslide masses can't be demonstrated. In terms of the actual landslide issues, the influencing factors of sliding velocity are quite complicated and the following factors have to be taken into account at the same time, including the change of the slope of sliding surfaces, the friction betwwen the sliding surface and landslide masses, the attributes of the structural plane which controls the movement of landslide masses and the rock materials, as well as the resistance factors in the sliding process. All of the above-mentioned factors have great impact on the change of landslides and the dynamic features of sliding velocity, which can't be ignored or too simplified in the calculation process.