Study On Evaluation Method For Foundation Stability Of Gravity Dam Based On Nonlinear Finite Element Method

Concrete gravity dam is an important type of dam widely used. But the presence of faults reduces the overall stability of the concrete gravity dam. With unique advantages, the non-linear finite element method has been developed rapidly in engineering, but it has not been fully used in the deep stability problem of gravity dam. Therefore, there are still many problems worth to research.Based on the comprehensive analysis of the deep stability method at home and abroad, this paper points out the problems of various existing methods. And this paper mainly carried out the following aspects of work.(1) The instability problem of a concrete gravity dam foundation is cited as an example in this paper. By using nonlinear finite element strength reduction method, three typical instability criteria (calculated non-convergent criterion, displacement mutation criterion, plastic zone penetrating criterion) are studied in numerical calculation way and the results are compared with traditional rigid limit equilibrium method, by which, the applicability and rationality of various instability criteria are discussed. The results show that the using of convergent criterion produces a large error, and the safety coefficient calculated by using displacement mutation and plastic zone penetrating criterion is close to that by rigid limit equilibrium method, which verifies the rationality of displacement mutation criterion and plastic zone penetrating criterion. Taking into account the applicability, simplicity and security, it is recommended that displacement mutation criterion and plastic zone penetrating criterion should be considered in the stability analysis of gravity dam foundation.(2) Under dynamic action, using the powerful contact nonlinear functions of ABAQUS to do the numerical simulation of the gravity dam of a hydropower station. Through analyzing and calculating of the deep stability problem of a typical dam section, the author concluded the deep development process and failure mode of instability of the dam section in the earthquake.(3) Comparing two different boundary conditions of foundation, massless foundation, and the dynamic response of viscoelastic boundary through engineering projects, it has shown that:compared with massless foundation, in the earthquake, considering the affect of radiation damping of foundation, the minimum value of the anti-sliding stability of the safety degree of the three characteristics of the interface is greater than the former, that is, the change of the security of the former is larger. Overall the result calculated by massless foundation model is safer.