2.5D Green's Functions And Its Application Of IBEM For TI Saturated Material

A great deal of observations and reports on earthquake damage at home and abroad indicate that complex topographies have a notable influence on seismic scattering,which is also an important subject studied in earthquake engineering and seismology.Most of the researches are conducted under the assumption of elastic medium.However,natural soils are a three-phase medium system containing soil skeleton,pore fluid and gas,and show obvious anisotropy during the process of sedimentary weathering.Therefore,the transversely isotropic(TI)saturated material model is adopted,which is more approximate to the real soil medium.At present,few researches about using indirect boundary element method(IBEM)to study the 3D scattering of complex topographies in TI saturated medium have been reported.Hence,introducing TI saturated medium model into the study of complex topographic effect has vital theoretical significance and practical values.The main works achieved are as follows:1.With the aid of the 3D exact dynamic stiffness matrix and direct stiffness method,the 2.5D dynamic Green's functions in the TI saturated half-space are derived,the applied loads contain the inclined uniformly distributed load and pore pressure.The correctness of the Green's functions is verified by comparing with the existing literatures.Numerical results for displacement,stress and pore pressure responses in the homogeneous and single layered TI saturated half-spaces are conducted.2.Based on the indirect boundary element method,the 3D scattering problems of obliquely incident elastic waves for canyon and lined tunnel in the layered TI saturated half-space are studied.The accuracy of the method is proved by contrasting with the existing results.Numerical examples for surface displacement and pore pressure of canyon,and stress concentration factor of the lining wall are studied.Parametric studies indicate that the transverse isotropy in saturated medium has significant influence on the 2.5D Green's functions,which also changes the displacement amplitudes and phases of canyon,the amplitudes and space distribution of stress concentration factor of tunnel.Meanwhile,the influence of incident frequency and incident angle of qP1,qSV and SH waves towards the scattering effects on complex topographies are also investigated.