Effects of Random Local Weaknesses in the Levels on the Reliability and Stability of Longtan RCC Gravity Dam

摘要

Longtan dam is a RCC gravity dam. The local weaknesses in the levels could be formed in the local range of special layers of some dam bodies because of the unpredictable reasons in the construction, such as the large rolled concrete storehouse surface, the continuous construction in the rainy season with high temperature, the unreasonable construction organization, the limit of capacity of equipments and the climatic conditions, etc. The effects of random local weaknesses in the levels on the reliability and the stability of Longtan RCC gravity dam are studied by the authors. Two following situations are mainly concerned: (1) Local weaknesses are in the levels of specific heights and three different distributions of weaknesses based on three different physical and mechanical parameters are considered at each height; (2) Local weaknesses appear in random heights. The stress and displacement of the dam with various static loads are computed by FEM on the conditions of weak levels transferring force or not. The limit equilibrium method and the strength reduction method are used to calculate the stability safety factors of given possible sliding levels. The method combining the gradient method in the generalized random space is used to calculate the reliability. The result shows that local weakness in the levels have little influences on stress and displacement of dam, but still have negative influences on the safety of dam. The stability safety factor and the reliability level of dam with the local weaknesses in the levels are all smaller than those of dam without weaknesses, and the longer local weakness is, the smaller indexes are.