Numerical Methods Of Concrete Dam Failure Process Based On Fracture Mechanics

Large concrete structures (such as concrete buildings, dams, bridges, docks, etc) are very important infrastructures in developing the economy and improving people’s quality of life. However, once those infrastructures crashed, it will cause huge casualties and property loss, so their safety must be guaranteed. In real-world projects, no matter how strict measures to control cracks, concrete structures are still working with cracks. Therefore, more and more researchers have drawn their attention to crack’s effect on the issues of structural security. Currently, structure designing is still based on strength theory, but it is difficult to reasonably reflect the effect of cracks which are bedded in the structures and the whole result of structures’crash process caused by cracks. Fortunately, fracture mechanics theory can be used to solve engineering problems associated with cracks as a substitutive theory of strength theory. In this paper, we comparatively study different methods to calculate fracture parameters of two-dimensional and three-dimensional elastic body which contain many forms of cracks and use extended finite element method, which used to deal with surface crack contact behavior under cyclic load, and cohesive crack model to research the effect of crack on concrete dam’s bearing capacity. The aim of this paper is to provide technical justification on fracture mechanic’s application to concrete dam’s analysis of crack and safety evaluation of concrete dam. The main contents and methods in this article are as follows:(1) For two-dimensional and three-dimensional cracks, we contrast the precision of J Integral method and interaction integral method to calculate stress intensity factor through general postprocessor of conventional finite element method and extended finite element method and the influence of grid size or the number of integral points. Where, J integral is a simpler method to solve two-dimension crack and three-dimensional planar crack. Interaction integral method is widely applied to solve stress intensity factor now, which based on reciprocal theorem. Through introducing appropriate auxiliary stress field and auxiliary displacement field, this method can handle two-dimensional curves and three-dimensional non-planar crack.(2) Extended finite element method permits crack through elements by inserting discontinuous displacement field or strain field into element. Through combining B-differentiable equations, which used to solve contact problems, and extended finite element method, we can easily define the space distance between contact points and impose contact conditions. This method can be used to research the impact of crack surface contact on stress and deformation distribution in dam body with crack under cyclic changed load.(3) Researching how to create concrete cohesive crack model and the application on notched beam concrete specimen and on the failure process of concrete dam with crack.(4) At last, researching the impact of different crack length on static bearing capacity of concrete structures with cracks.