Thermo-hydro-mechanical coupling effects on wave propagation and strain localization in a fully saturated softening porous medium
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We investigate analytically the thermo-hydro-mechanical (THM) coupling effect on the length scale of fully saturated porous media under the non-isothermal condition. By extending the previous work on stability and dispersion analysis on isothermal porous media, we analyze the stability of the system of equation subjected to harmonic perturbations and derive the expression of length scale and phase velocity of the non-isothermal porous media as a function of mechanical, hydraulic and thermal material properties. We prove that the new expression of length scale is consistent with the classical results under limited conduction such as undrained, drained, adiabatic and isothermal conditions. Both one- and three-dimensional wave propagation simulations are conducted using a stabilized mixed THM model to compare the results from stability and dispersion analysis. Our analytical results and numerical experiment both indicate that while permeability and thermal conductivity may affect the thickness of plastic zones, introducing multi-physical coupling effect alone does not guarantee the cure of mesh dependency when strain localization occurs. Keywords: thermos-hydro-mechanical coupling effect, porous media, wave propagation, stability, dispersion, internal length scale.