Application Research Of Dda In Stress-distortion Analysis Of Rockfll Dam

The DDA is a new kind of method for stress and deformation analysis which aims at non-continuous medium, and it is suitable for calculation of static and dynamic discontinuous large deformation. The DDA divides model into units by using structural surfaces of objective existence, whose shapes are close to the actual structure, and there are less and accessible parameters needed in the process of DDA computation. This paper regards the rockfill dam as a collection of rockfill particles, and analyses the stress and deformation of rockfill dam from its microscopic composition. Several typical non-continuum numerical methods are firstly introduced in this paper, at the same time, the advantages and disadvantages of these algorithms are pointed out. Then the author studies how to generate automatically the rockfill particles of arbitrary shapes in the computer. According to the characteristics of plane strain of rockfill dam, the flexibility sub-matrix in the original DDA is modified, and interface or improvement is also established to every part of the program. Besides, the value ranges of two important parameters of the spring stiffness and step displacement are explored. Finally, numerical simulations of a small and homogeneous rockfill dam in construction stage and water phase are conducted, what follow are the stress and deformation results. The frondose research contents of this paper are as follows:(1) Because of arbitrary shapes and random locations of rockfill particles in rockfill dam, the author explores a numerical simulation method for random distribution of rockfill in depth, and a procedure for automatic generation of them is written.Particles generated by this method have random positions and arbitrary shapes which different from each other, and can satisfy the requirements of a given gradation. This lays the foundation for further calculation of the stress and deformation of rock-fill dams.(2) There are hundreds of thousands rockfill particles, so the original DDA program needs people to enter lots of geometrical and physical information about joint surfaces and external loads withstood by them to generate block units and calculate their movements and deformations. In order to realize automation of this tedious and error-prone process of manual input, interfaces to pre-processing and computing in the original DDA program are established, which simplify the calculation process effectively. In addition, the author improves the post-processing way in the original DDA program, adopting more intuitive cloud to display results.(3) Two important parameters of spring stiffness and step displacement in the DDA are not only related to material of model, but also effect the calculative result. Through setting up lateral restraint compression model of rockfill material by the DDA, this paper repeats the experiment to analysis how spring stiffness and step displacement affect the results in different range, and finally discovers the appropriate scope of the two parameters to calculate rockfill in this paper.(4)On the basis of the above work, the author applies the DDA to simulate the construction period and water phase of one20m high small homogeneous dam, and calculates and validates the stress and deformation results to indicate that the simulate results are satisfactory, so far, a new method is proposed to analyze stress and deformation of rockfill dams.