Coupled thermo-hydro-mechanical response of saturated asphalt pavement

This study aims to characterise the coupled thermo-hydro-mechanical properties of the saturated asphalt pavement under the vehicle load, the thermal deformation and thermoviscoelasticity of the asphalt layer, and the pore water pressure in the voids of the asphalt layer. A thermo-hydro-mechanical model (THMM) was proposed by coupling the governing equations of triple physics of thermal, hydraulic, and mechanical fields. Based on the identification of circular dependence of the above triple physics, weak forms of the coupled governing equations were incorporated into a weak form equation-based finite element software package. The effectiveness and accuracy of the THMM were validated from the perspective of mechanical performance of the asphalt mixture, temperature profile of the asphalt pavement, and hydro-mechanical performance of the asphalt pavement, respectively. Results show that the thermal deformation and thermoviscoelasticity are both vital for performance prediction of the asphalt pavement; the thermal contraction and thermal tensile stress appear in the cool-down asphalt pavement (pavement temperature decreases), and the thermal expansion and thermal compressive stress emerge in the heat-up asphalt pavement (pavement temperature increases). The pore water flows outside of the pavement under the vehicle load and flows back to the pavement when the vehicle load travels far away. Compared with the dry asphalt pavement, the pore water can decrease the effective stress induced by the vehicle load, but it will increase the residual stress when the vehicle load travels away. For the selected undamaged asphalt pavement, the smaller relaxation modulus comes from higher temperature and produces higher hydraulic pressure in the saturated asphalt layer, and vice versa. The maximum differences between the vertical strains under the vehicle load in the saturated and dry asphalt pavements lies in high temperature period of one day, and there are almost no differences when the vehicle loads travels far away. The pore water in the saturated asphalt pavement contributes well to the temperature distribution and generate temperature gradient in the transverse direction of the asphalt pavement.