Study On Reliability Of Slope Stability Of High Rockfill Dam

Rockfill dam takes up an important place in hydraulic power engineering. The slope stability is the key issue of the design of rockfill dam. Therefore, the slope stability of rockfill dam is significant.The dam materials are natural materials, and discreteness and uncertainty of materials strength are remarkable. Although safety factor meets the regulatory requirement, the slope may be unstable. That is single safety factor method can not consider the variability of material strength on slope stability, which makes the stability analysis is imperfection. So the slope reliability analysis is essential. Reliability analysis of rockfill dam slope can consider the discreteness and variability of strength of dam materials, which is a beneficial complement for traditional safety factor method.The slope stability of high rockfill dam is analyzed in this thesis. Firstly, the material parameters of rockfill dams over 100m in height are collected in China, including nonlinear strength of rockfill material and linear strength of corewall material. Then, distribution type, mean value, standard deviation and variation coefficient of material parameters are obtained for main rockfill, secondary rockfill and corewall by mathematical statistical method. Lastly, the relation about correlation coefficient and reliability index is discussed.Based on statistical parameters, reliability indexes of faced rockfill dam and core wall rockfill dam are calculated. The height of dam varies from 100m to 350m. For core wall rockfill dam the slope ratio varies from 1:1.8 to 1:2.0. For concrete faced rockfill dam the slope ratio varies from 1:1.3 to 1:1.6.3Dstab program developed by our team is used to compute the safety factor and reliability index. Simplified Bishop Method is used to calculate the safety factor. Particle Swarm Optimization (PSO) is applied to search for the critical slip surface. And First-Order Second-Moment (FOSM) method is used to analyze the reliability. The results show that safety factor and reliability index decrease with the increase of height. In a similar way, the reliability index will decrease with the increase of slope ratio under the same height. The stability index of stabilization seep time is greater than that of the finish time. In order to estimate the stability index of rockfill dam rapidly, the fitted formulas consisting of dam height, slope ratio, seismic intensity are given based on results. And the maximum relative error of fitted result is also given.