The Research On Seismic Wave Propagation And Scattering Of Three-dimensional Poroelastic Sites With Single-porosity And Double-porosity Medium

In recent years,the research on the theory of seismic wave and related problems in double-porosity medium has been paid more and more attention by domestic and international experts and scholars,especially the problem that the propagation and scattering of elastic wave in single-porosity and double-porosity medium has always been a challenge for the scientific community.The research topics have a great significance in both seismology,earthquake engineering,geophysics and other disciplines.In the past few years,most research focused on the scattering of elastic wave in single-porosity and many scientific research results have been achieved.Actually,there are intricate matrix fluids,pore waters and undercurrents in the real geotechnical layers,and the propagation characteristics of elastic wave in fluid-saturated rock layers are significantly different from those in dry soil elastic sites.Therefore,the propagation and scattering of elastic wave in single-porosity and double-porosity medium is more practical.The focus of this paper is on the propagation and scattering characteristics of elastic wave in a three-dimensional saturated site with single-porosity and double-porosity medium.Based on the Biot’s theory of single-porosity and the double-porosity model found by Berryman,a basic solution method based on spherical wave potential function of SWP-MFS is proposed for different medium sites.Firstly,combining the constitutive model of single-porosity medium,the spherical wave potential functions of two kinds of compression wave（P₁,P₂）and three kinds of vector shear wave are used to derive the displacement,stress,relative displacement of fluid and dynamic pressure function of pore fluid.Then,the scattering wave field is constructed,and the boundary integral equation is established based on the boundary conditions and solved by the point.Secondly,based on the complex structure of the underground fissure layer,with reference to the theory of double-porosity medium with cracks（causing compression wave P₃）,the dynamic solution Green’s function of the spherical wave potential function in the underground infinite domain is taken as the basic solution to develop the double-porosity saturated two-phase.The SWP-MFS of the three-dimensional wave problem of the medium is used to study the seismic wave scattering of the double-porosity saturated medium.The correctness and stability of the proposed SWP-MFS in the two mediums are tested.Finally,according to the scattering characteristics of elastic wave and dynamic concentration of single/double-porosity medium,the diffraction and scattering of seismic waves by underground inclusions and underground caverns are studied.The effects of different incident modes,incident frequency and boundary drainage conditions on the seismic response of the scatterers are analyzed.The results of site interface displacement,hoop stress,matrix fluid pressure and pore fluid pressure amplitude are given and analyzed theoretically.The research results show that SWP-MFS,as a new algorithm and practical method,can solve the scattering problem of elastic wave in two saturated mediums.At the same time,it is also a new solution for the fluctuation problem of saturated inhomogeneous medium and provides theoretical basis for geological verification of saturated sites,seismic engineering and seismic zoning.