Scattering Of Elastic Waves By Group Cavities In Layered Poroelastic Half-Space

The analysis of surface motion due to underground group cavities in Layered Saturated Half Space is important both in theory and engineering. According to the practical Biot's equation, Liang Jianwen,You Hongbing derived the general solutions of the wave by introducing wave potentials. Then exact and symmetric dynamic-stiffness matrices of a layered saturated soil and half-space are derived. Then they derived the Green's functions for distributed loads or pore pressure acting on inclined line in a layered poroelastic, which resolved the key problems in wave scatting by local soil conditions and dynamic soil-structure interaction by using the indirect boundary element method(IBEM). How to use the theory analysis elastic waves scattering by canyon group is the main problem solved by the paper.Scattering of plane P wave around canyon group in Layered Saturated Half Space is studied by IBEM and the effects of porosity, drainage condition, and the distance between the two cavities, etc. on the wave scattering are discussed. It is show that, for incident P wave, the horizontal displacement amplitudes is larger for the dry poroelastic case and the surface vertical displacement amplitudes are larger for the saturated case. For small porosity , the drainage condition has little influence on the surface displacement amplitudes,for large porosity,the effect of drainage condition cannot been ignored. The surface displacements in the case of undrained condition are larger than the corresponding displacements in the case of drained condition. When the frequency is lower and the distance is closer, the interaction between the two cavities is obviously. As the frequency and distance increase the interaction between the two cavities decreased gradually.Scattering of plane SV around canyon group in Layered Saturated Half Space is studied by IBEM and the effects of porosity, drainage condition, and the distance between the two cavities on the wave scattering are discussed. What different from plane P wave is that SV wave has the critical angle. Both he porosity and drainage condition have an obviously effects when the incident angle nearby the critical angle. Generally, the vertical displacement amplitudes are larger for the dry poroelastic case and the surface horizontal displacement amplitudes are larger for the saturated case. The effect of distance between the two cavities on scattering is same with the plane P wave.