Wave Propagation And Reflection From The Free Surface In Double-porosity Media

The bulk waves in double-porosity media and the reflection of PI wave at the free permeable and impermeable surfaces are theorectically derived and solved. The variations of the displacement reflection coefficients of the reflecting waves with the incident angle under different surface boundaries, as well as the dispersion and attenuation characteristics of the four kinds of bulk waves, are numerically studied. The results show that:(1) P1、P2、P3and S wave are of dispersion and attenuation. Thereinto, P1wave propagates fastest with lowest attenuation, and P3wave attenuates fastest with lowest propagation velocity.(2) With the increase of incident angle of P1wave, the displacement reflection coefficients of the reflecting P2、P3and S wave increase at first then decrease, but the case of the reflecting P1wave is just opposite.(3) The permeability of the surface has distinctive effects on the displacement reflection coefficients of P2and P3wave with slight effects on P1and S wave. Nevertheless, whether the surface is permeable or impermeable, the changing tendency of the displacement reflection coefficients is consistent.