Abstract：The mechanism of the deformation of Xiluodu Valley is still controversial，which is a key problem in the current engineering field. Based on the comparative analysis of Jinping I and Xiluodu valley deformation，the valley deformation of Xiluodu shows the feature of large value，large scale and integration. In this paper，we adopt the elasto-plastic method of deformation reinforcement theory as the approximation of visco-plastic method，and take the pore elastoplastic effective stress and the hydrogeological structure of Xiluodu Reservoir area into account. The key location which controls the Xiluodu valley deformation is studied by analysing the unbalanced force，which drives the plastic deformation of structure. The results indicate that the unbalanced force caused by the increase of pore pressure after impoundment is mainly concentrated in the basaltic layer and the interlayer dislocation plane at the bottom of the valley，that could drive the rock mass to produce large-scale deformation along the layers and may be the primary mechanism of the structural valley deformation of Xiluodu.
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2023, Vol. 42 
