Dynamic Analysis Of Fluid-unsaturated Porous Media By Using Explicit Finite Element Method And Application

The dynamic response of unsaturated porous media research has important academic value in the following fields,such as civil and environmental engineering, geophysics, petroleum engineering, chemical engineering and biological engineering, etc. This paper selected the Wei’s unsaturated porous media governing equation based on the theory of mixtures with interfaces, considering the complexity of the dynamic responses of unsaturated porous media, the analytical method only in the specific boundary conditions can solve this problem, so the numerical method was choosen in this paper. In order to solve the unsaturated porous medium governing equation quickly and efficiently, the explicit finite element method which no need to slove the linear equations was choosen.In this paper, dynamic response analysis of unsaturated porous media is carried out as follows:(1) Establish the explicit expressions of dynamic response analysis of unsaturated porous media.In the form of matrix representation of Wei presented unsaturated porous media wave equations,by making use of Galerkin method write a Galerkin weaken type. Use the decoupling technology to solve the explicit expressions of dynamic response analysis of unsaturated porous media.(2) Based on the explicit expressions of dynamic response analysis of unsaturated porous media, establish the explicit finite element calculation program.With the reference of saturated porous media finite element numerical calculation method,we establish the explicit finite element calculation program in the two-dimensional coordinates. Firstly introduce the artificial boundary,then give the calculation area, input the initial displacement field or initial force field, divide the area calculation into finite element mesh, compute nodes mass, stiffness,damp, forces and the dynamic responses of nodes.(3) Numerical verifications for the unsaturated porous medium finite element program (PW-DEF).Use three methods to verify the results:the first method is to degard unsaturated porous to saturated porous;the second method is to replace gas phase parameters with liquid phase parameters,assuming the pore is full of two liquid phases which have the same parameters;the third method is to verify the dynamic response of unsaturated porous meida. To verify the correctness of the method,The calculation results obtained with the three methods are compared with the analytical solution.(4) Use the application of the dynamic analysis of fluid-unsaturated porous media by using explicit finite element method to analyze the dynamic responses of unsaturated soil.we get the following conclusions:1)The saturation has different influence on the displacement of each phase in different forms of loads. The displacement of solid phase has the same changes no matter what kinds of load forms, It will decrease with the increasment of saturation.The displacement of liquid phase has the different changes in the two kinds of load forms,It will decrease with the increasment of saturation in the point load,but it will increase with the increasment of saturation in the uniform load.2)With the increasement of vibration frequency,the displacement of each phase will decrease,but the attenuation of dispalcement will increase.The change of frequency will also affect the influence of the displacement by saturation.3)The attenuation of the horizontal direction is faster than the vertical direction.4) The rang of vibration response will increase with the increasement of virbation frequency in both rigid foundation and flexible foundation. Compared to the flexible foundation the displacement of the solid phase is more obvious.