Abstract: Jinping II Hydropower Station is an important cascade hydropower station on the Yalong River in Sichuan Province. The hydropower station region is a typical V-shaped river valley morphology with high grand mountain and deep gorge. Tectogenetic movements, including Indo-China movement, Yanshan movement and Himalayan movement, made the region preserve much horizontal constitution stress. But, the corrosion effect of the Yalong River leads to figure the V-shaped valley and release of constitution stress. For understanding the function of inter dynamical geological process and outer dynamical geological process to current geostress, a new nonlinear initial geostress back analysis method is presented, which integrates the ground abrasion simulation, elastoplastic calculation and neural network inversion. The method takes the constitution order process into account to some extent by elastoplastic calculation and simulates the ground abrasion process by surface excavation. The model is verified by two ways. One is the comparison between measured stress, and inversed stress in the same position; the other is the broken behavior of cavern rock. The results indicate that the method is reasonable.

Key words: geostress, nonlinear inversion, ground abrasion, tectogenetic movement, neural network, Jinping II Hydropower Station