Dynamic characteristics analysis and seismic safety evalution for Madushan Gravity Dam

According to the engineering geological condition of Madushan RCC Gravity Dam, the 3-D finite element model of the joint effect of the dam and its foundation is established to analyze dynamic characteristics and evaluate seismic safety of Madushan dam. In this paper, dynamic time history analysis method is applied to calculate the dynamic response of the roller compacted concrete gravity dam so as to obtain the seismic acceleration response, displacement and stress response and their distribution. The foundation stability against sliding is analyzed by the point safety factor method and the strength reserve safety factor method. The calculation shows that, in VII seismic fortification intensity, the maximum displacement response of the dam is 13.18mm, the maximum stress response is 2.264MPa, the maximum acceleration response is 3.628m/s², magnification of 3.69, thus the strength of dam meets with the requirements. Meanwhile the foundation point safety factors of the overflow dam are all greater than 1, no continuous foundation failure surface, and the dam's strength reserve coefficient is 3.68. So the dam meets with the safety requirements.

I. Introduction

Madushan hydropower project is located at the lower reaches of River Honghe, mainly for generating electricity, flood control, navigation, water supply and other comprehensive benefits. As to the gravity dam, the maximum height of the dam is 107.5m, the length of the dam crest is 353.0m. The design seismic intensity of the dam site is VII degree. The rock of the dam foundation is mainly composed of the weak weathered rock, containing a small amount of completely and strongly weathered rock. The depth of the upper floor line of weak weathered rock: is 10–20m for the left bank, 10–25m for the river bed and 30–50m for the right bank.