Abstract

There are three 300 meters level arch dams in China. Among them, Jinping1 and Xiluodu showed significant valley width reduction in the process of initial impounding. This phenomenon is characterized by two different deformation modes, and difficult to analyze with conventional seepage and stress analysis method. The valley width deformation is the macroscopic manifestations of the deformation of fracture or structural surface and is irreversible plastic deformation. The start condition of structural plane deformation is to meet Mohr Coulomb strength criterion. Mohr Coulomb criterion can be used to study the mechanism of valley width deformation. By analyzing the monitoring data, valley width deformation can be divided into two modes: deformation of the near bank slope and overall deformation. Based on continuum mechanics, poroplasticity theory is adopted to explain the valley width reduction of Jinping1, the result of which is in good agreement with the monitored data. Based on noncontinuum mechanics, the rigid limiting equilibrium method is adopted to try to explain the valley width reduction of Xiluodu. Finally, the difference of the influence of the two valley deformation modes on the dam is analyzed. Although the magnitude of valley width reduction of Jinping1 is limited, it can produce new stress concentration on the dam body. However, for the valley width reduction of Xiluodu, although the magnitude of valley width reduction can be large, the effect on the dam stress is not significant.

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