This study aims to clarify the reflection-transmission behavior of interfacial waves in saturated porous media under the coupled effects of thermal conduction, viscoelastic dissipation and nonlocality.
Based on nonlocal thermoviscoelastic theory, a reflection-transmission model is developed for a plane P-wave incident on the interface between two saturated porous media. Analytical expressions are derived for the amplitude ratios and energy reflection coefficients of all reflected and transmitted waves. The effects of relaxation time, medium temperature and the nonlocal parameter are then systematically investigated.
An increase in the angle of incidence weakens the normal energy transmission across the interface and facilitates the conversion of the incident P wave into the slow compressional wave and shear wave. At f = 1,000 Hz, the inertial coupling between the solid skeleton and pore fluid becomes more pronounced, giving rise to a more significant P2-wave response. At higher frequencies, however, the thermal wave response is strengthened, whereas the shear wave is attenuated owing to viscoelastic dissipation and viscous damping of the pore fluid. The influence of the relaxation time varies among different wave modes and is particularly marked for the reflected P2 wave, transmitted P2 wave and transmitted thermal wave, indicating that its primary role lies in regulating slow compressional and thermal wave propagation through modifications of viscoelastic dissipation and interfacial mode conversion. Temperature exerts only a limited effect on the fast compressional mode, but its impact on the slow compressional mode is considerably more pronounced; specifically, an increase in temperature suppresses the reflected P2 wave while enhancing the transmitted P2 wave. A reduction in permeability inhibits the propagation of the reflected P2 wave and thermal wave, while simultaneously amplifying the transmitted P2 wave and the shear-wave responses on both sides of the interface; by contrast, the P1 wave is comparatively insensitive to changes in permeability. The nonlocal parameter exerts only a minor influence on the fast compressional wave and thermal wave, but the slow compressional wave and shear wave exhibit greater sensitivity, with the transmitted P2 wave being enhanced and the transmitted shear wave being suppressed.
This study develops an analytical model for P-wave reflection and transmission at the interface between nonlocal thermoviscoelastic saturated porous media and reveals the different roles of relaxation time, temperature and nonlocality in interfacial mode conversion and energy redistribution.
