3D Viscous-spring Artificial Boundaries Of Infinite Saturated Media

Under the effects of strong shock, earth dam, and soil slope, their foundations will undergo liquefaction instability. Therefore, the soil should be regarded as being composed of soil skeleton and pore water, when evaluating seismic resistance safety. The dynamic analysis shall not only show the displacement time history of the soil skeleton, but also calculate the change time history of the pore water. Different from the viscous-spring artificial boundary of the single-phrase solid structure, in regards to the artificial boundary of saturated soil except for the displacement boundary conditions to be handled, the spread of the pore water pressure in the artificial boundaries was well considered.This study established a dynamic principle of virtual displacement of a 3D saturated foundation with a viscous-spring boundary, based on the research results of the current artificial boundary processing method, and developed the FORTRAN programs for solving a three-dimensional dynamic consolidation equation saturated media with viscoelastic artificial boundaries by means of the Finite Element Program Generator(FEPG), also investigated the dissipation processes of ground displacement, velocity, acceleration and pore water pressure in soil foundation under the impact load, sudden-loading and seismic loading. The main research contents are as follows:(1) Based on Zienkiewicz’s assumptions that the earth is a two-phase body composed of solid skeleton and fluid media, ignoring fluid compression wave, the u-p formulation of saturating media consolidation equations are taken as the basic equations. According to the equivalent relationships of stress and displacement on spherical wavefront and artificial boundary, the normal and tangential spring coefficients, damping coefficient and flux boundary conditions are derived.(2) The weak form of three-dimensional dynamic consolidation equation that plus viscoelastic artificial boundary of saturated medium is established based on virtual displacement principle. The seismic input of saturation media on viscous-spring artificial boundary is proposed based on the principle of effective stress;(3) According to established dynamic consolidation equations in the form of weak, T The script files are written according to a finite element language. Based on FEPG the program source codes are generated, and the correctness of the established equations and procedures are verified. The influence of pore pressure absorbing boundary and media damping, and dissipation processes of displacement, and pore water pressure in soil foundation under seismic loading are investigated.