Simulating and predicting river valley contraction induced by Baihetan dam impoundment

In recent years, the issue of river valley deformation in domestic hydropower projects has garnered increasing attention, particularly the phenomena of valley contraction and expansion, which pose significant threats to dam safety. However the understanding of these deformation mechanisms remains limited. This study focuses on the Baihetan reservoir, analyzing monitoring data of river valley contraction (RVC) in the dam area before and after impoundment. The mechanism of RVC are discussed, and an elastic-creep calculation model is used to predict the development trend and convergence value of RVC. Our findings indicate that the deformation mechanism of the RVC process before and after the impoundment are identical, originating from rock mass creep. The RVC process and its convergence value are determined by the rock mass creep parameters. The entire RVC process, strating from slope excavation can be simulated using two-stage creep parameters. The results suggest that basalt creep deformation is the primary cause of RVC. Slope excavation initiates the first stage of rock creep and RVC, while the reduction in basalt creep parameters following impoundment triggers the second stage of rock creep and RVC.