Thermo-osmosis and mechano-caloric couplings on THM responses of porous medium under point heat source

Abstract

The influences of thermal gradient on the fluid flux (thermo-osmosis effect) and pore-pressure gradient on the heat flux (mechano-caloric effect) are usually ignored in the thermo-hydro-mechanical (THM) analysis of porous media. However, this assumption could have significant impacts on the analyses of geomaterials of relatively low permeability. In this paper, a point heat source was deeply buried in a saturated porous medium where the thermo-osmosis and mechano-caloric effects were considered. Laplace-Hankel transforms were applied to the linear equations governed by porothermoelasticity and to obtain the analytical solutions, the volumetric strain connected the displacements with the pore pressure and the temperature change. By applying the Laplace-Hankel inversion, the solutions in the real domain were obtained and verified by the existing results. The numerical results showed: (1) in geomaterials of low permeability, the mechano-caloric effect on the temperature change, heat flux and thermal gradient was negligible but the thermo-osmosis effect caused negative pore pressures which increased the effective stress of porous medium; (2) the thermo-osmosis effect pronouncedly drove the outflow of pore fluid away from the heat source which would be balanced by an inflow of pore fluid toward the heat source caused by the negative pore pressure.