Analysis of reservoir slope deformation during initial impoundment at the Baihetan Hydropower Station, China

Abstract

Reservoir slope deformation induced by impoundment poses a threat to the safety of high-arch dams, which has received widespread attention in recent years. With an arch dam height of 300 m class, Baihetan is the largest hydropower station under construction. However, the theory behind its reservoir slope deformation under complex hydrogeological conditions is still an open question. In this study, a numerical model was developed to describe the complex seepage field at the dam site before and after impoundment. Furthermore, the numerical simulation of reservoir slope deformation was conducted based on the effective stress principle. The monitoring data collected during the initial impoundment of Baihetan validated the numerical model. Based on that, the spatiotemporal deformation law of the reservoir slope and its main controlling factors were analyzed. The results indicate that the contraction of the upstream valley is mainly caused by the reduction of the effective stress of the reservoir slope, the high and steep topography formed by the extensive excavation, and the weakening of structural planes. The effective stress reduction caused by the bypass seepage, and the stress adjustment may be the main reason for the deformation of the downstream reservoir slope. In addition, structural planes distributed in the dam foundation play a particular control role in the deformation of the foundation slope. This study systematically characterized the impoundment-induced reservoir slope deformation features of Baihetan and discussed the possible deformation mechanism, providing an essential reference for evaluating the structural safety of the dam during operation.