Deformation mechanism and model of river valley contraction of the Xiluodu reservoir, China

The reservoir impoundment may induce various geological problems, such as landslides, reservoir-induced earthquakes, and karst collapse. The continuous river valley contraction (RVC), also known as valley shrinkage, has been detected at the Xiluodu Dam since the reservoir impoundment. This study investigated the mechanism of the RVC and the vertical deformation of the reservoir bank. It is found that the RVC and the vertical deformation come from the expansion of the limestone and basalt formations. The expansion is induced by the substantial increase in the pore water pressure after reservoir impoundment. A novel analytical and inversion models are established according to the proposed deformation mechanism to calculate RVC. Using the Monte Carlo sampling method, the development of RVC is predicted by the analytical model. It is found that the influence of limestone on RVC is more significant than that of basalt. Using the Markov chain Monte Carlo method, the parameters of the inversion model are obtained based on the field monitoring data, and the development of RVC is predicted. The prediction results of RVC agreed well with the observation data, and the convergence value is between 85.78 and 101.38 mm. This work deepens the understanding of the RVC and provides an important reference for engineers to evaluate dam safety.