Abstract: For a high arch dam, significant reservoir bank deformation during its impoundment has been observed and it is diversified in magnitude and variation, which threatens its working condition and long-term safety owing to the nature of its statically indeterminate structure. This paper presents an analysis of the reservoir bank deformation and its spatial and temporal distributions through examining the data of valley width, slope interior and reservoir plate for the Baihetan dam. The components of water level, temperature and aging are separated by developing a multiple stepwise regression model of valley width deformation. An elastic-plastic finite element model is constructed using the effective stress principle of fractured rock mass; the valley deformation at the initial impoundment stage of 800m is calculated. The monitoring data show that most of the survey lines are basically in shrinkage deformation, and all of them have a certain correlation with the rise in the reservoir impounding stage. Along the river, the upstream sections feature a valley width deformation larger than that of the downstream ones. Survey data from high to low elevations of a valley section manifest a decreasing trend in the shrinkage deformation of valley width. The interior of the valley slope is in tension, and most of the reservoir plate undergoes subsidence. The results of multi-variate regression analysis and numerical calculations show that for the upstream sections, the calculated valley width deformation based on effective stress at the 800m stage are close to the measurements, and both are the same in spatial distribution patterns. It can be considered that the change in effective stress is the main factor affecting initial reservoir bank deformation.

Key words: initial impoundment, reservoir bank deformation, influence factor, effective stress, numerical simulation