Study on mechanism of valley creep deformation of high arch dam during impoundment

• 1、China Institute of Water Resources and Hydropower Research, China Institute of Water Resources and Hydropower Research, Beijing 100038
• 2、State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin，Beijing 100038

Abstract：The reduction of valley width has been found in Some high arch dams after water storage at present in China, which affects the current working behavior and long-term safety of high arch dams. In this paper, the regression analysis of the valley deformation process at each monitoring point of Xiluodu arch dam was carried out, so valley deformation is decomposed as deformation caused by instantaneous change in water level, deformation caused by temperature and time effect deformation. Based on the results of the regression analysis, the effects of reservoir pressure, bedrock temperature and hydrogeological condition on valley deformation were studied respectively with finite element method. The main reason of continuous reduction of valley width of Xiluodu arch dam is revealed by analyzing the different impact on valley deformation under each factor. The research shows that changes of hydraulic pressure and bedrock temperature could cause a certain valley deformation, which is much smaller than the measured deformation, and is not the main cause of valley deformation of Xiluodu arch dam. Valley deformation is largely the time effect deformation caused by the change of hydrogeological conditions in the near dam area, which presents as the creep deformation of the structural surface along the interlayer fault zone. The driving force of valley deformation is high geostress, and the trigger of vally deformation is material degration of the faults and effective stress decreasing.

Keywords： high arch dam valley deformation creep trigger mechanism