SPH-Based Numerical Simulations On Soil Large Deformations

It is very important to know the behavior of soil subjected to large deformation for design of structures and prediction of geodisasters. In practical engineering, the soil usually exhibits large deformation coupled with different mechanisms: fluid dynamics and elasto-plastic dynamics. This makes it hard to exactly predict all deformation characteristics in one method, particularly for the extreme deformation. To solve the difficulty, it is necessary to capture the large deformation performance of the soil in the sense of coupled mechanics, instead of single method.The main study of this thesis is to apply Smoothed Particle Hydrodynamics(SPH) method in solving soil large deformation problems. As a meshfree, Lagrange, particle method, SPH has its own particular characteristics with some special advantages over the traditional grid-based numerical methods, especially in the application of large deformation analysis. The research work is completed as follows:(1)The state-of-art of the soil subjected to large deformation is summarized in this paper. Combined with dynamical characteristics and engineering demand of large deformation analysis in practical engineering, the problems and shortcomings of existed numerical methods are pointed out.(2) As SPH method is a newly emerged method for the applications in the fields relative to Geotechnical Engineering, the basic concept is introduced in detail. It has been shown out that SPH has two key steps, Fuction Approximation and Particle Approximation. In SPH method, the problem domain is represented by a set of arbitrarily distributed particles. So the SPH method is able to deal with large deformation. And the SPH formulations of fuild mechanics and elasto-plastic mechanics are presented.(3) Some numerical aspects such as artificial viscosity, particle searching method and smoothing kernel function are described in the aim at improving SPH calculation precision. Based on the discussion, Verlet neighbor list is selected as the particle searching method and one kind of cubic spline interpolation function as the smoothing function. Then the SPH programs for soil large deformation are developed in FORTRAN language.(4) In order to verify the SPH programs, the dam break and simple shear test on completely elastic body are imployed in the numerical simulation. The calculation results show good agreement with the relative test data and theoretical solution; still the results can get the moving information of every particle.(5) In the aim at solving the problem in soil large deformation with two different methods, the Bingham Fluid constitutive model combined with the Mohr-Coulomb failure criterion and modified Cam-clay model are introduced in SPH program respectely. The ground flow model test and soil undrained simple shear test are simulated in the programs, and the numerical result and test data are compared in detail, they show good agreement with each other.In this thesis, the elasto-plastic mechanics and fluid dynamics are introduced in the analysis.Based on SPH method, the fuild and elasto-plastic programs are developed for soil large deformation. The SPH programs are verified and validated through large calculation comparison with test data and theoretical solution. In the finality, based on the conclusions of the whole work, the problems requiring further studies are discussed.