Three-Dimensional Viscous-Spring Boundaries In Time Domain And Dynamic Analysis Using Explicit Finite Element Method Of Fluid-Saturated

For the dynamic analysis of some important complex structures such as high-rise, high dam, nuclear power station and so on, the wave propagation from structure into infinite foundation should be considered.The saturated porous media is general existed in the nature, for example, the saturated soil, which is made up of solid skeleton and pore liquid fluid medium. If the dynamic interacting between the previous two part is concerned, using the saturated soil theory analyzing is more appropriate and scientific than using the single medium analyzing. As the complex of the saturated porous media theory and the difficulties of the disposing in mathematics, the analytic solution of saturated porous medium dynamic response is topical the simple boundary condition. To the complex geometry and the near field heterogeneous and nonlinear condition, numerical method is the effective mean. In the dynamic finite element analysis of saturated porous media in whole space or half-space, a finite model numerical method is usually selected for computing. To reflect unrestricted region energy radiation effect, it is necessary to input the supposed artificial boundary and computing method. The artificial boundary disposing means and computing means is largely influenced the computing accuracy. As the decoupling of time and position, explicit finite element combining local artificial method is proper to the previous complex near field wave-motion problem's solving. The main studies in this dissertation are listed as follows:1. An approximate spring-dashpot three-dimensional artificial boundary conditions of saturated porous media are presented. It is shown that the normal and tangential wave stresses of the solid phase on the boundary are proportional to displacement and velocity, and the pore fluid has only normal wave stress which is proportional to it's velocity on the artificial boundary. Therefore, the continuously distributed springs and dashpots can be set on the artificial boundaries in the normal and tangential directions to absorb the energy of outgoing waves. The wave motion input can be realized by applying equivalent loads on the artificial boundaries.2. According to the dynamic analysis of saturated porous media by using explicit finite element method proposed by professor chenggang zhao, this paper develops finite element method which could solve the three-dimensional problems, and develops finite element programme named PT-DEA.Numerical example indicate that the proposed three-dimensional viscous-spring artificial boundary enjoy good accuracy and good stability.Numerical example indicates that the accuracy and good stability of the proposed three-dimensional viscous-spring artificial boundary correspond with that of existing analytical, extended finite element solution and the second-order transmitting boundary.The analysis of the saturated porous medium dynamic response indicates that the combination method of the explicit finite element method and the three-dimensional viscous-spring boundary is effective.