THE COUPLED THERMO-HYDRO-MECHANICAL DYNAMIC RESPONSE OF SATURATED POROUS SUBGRADE CONSIDERING PERMEABILITY ANISOTROPY BASED ON FRACTIONAL ORDER THEORY

Due to the difference in deposition and stress state, the anisotropy of natural soil is obvious. Based on Biot’s wave equation, Darcy’s Law, Lord-Shulman generalized thermoelastic theory and Riemann-Liouville integral operator, this paper adopts the normal mode analysis method to study the influence of permeability anisotropy on the saturated foundation with coupled thermo-hydro-mechanical multi-field under external loads. The normal mode analysis is a method to derive the analytical solution by using the weighted residual. By this method, the influence of anisotropy parameters and fractional order parameters on the physical variables under study is analyzed. The influences of the fractional derivative and the anisotropy of permeability coefficient on the physical variables such as dimensionless excess pore water pressure, vertical stress, vertical displacement and temperature in the foundation are mainly analyzed when the thermal load and mechanical source are considered in the upper surface. In addition, when the fractional derivative and the anisotropy parameters with the same physical meaning are taken as the same parameter, the anisotropic foundation model can be completely degraded into an isotropic saturated poroelastic foundation, which verifies the rationality of the foundation model. The results show that the variation of permeability anisotropy has obvious influence on all the physical variables except the dimensionless temperature when the thermal load is considered. It can be clearly seen from the curve with peak value that as the anisotropy of permeability coefficient increases, the peak value of the curve moves deeper to the foundation; however, it can be seen from the curve without peak value that as the anisotropy of permeability coefficient increases, the attenuation rate of the curve slows down. The research results can be widely used in the field of geotechnical engineering and have certain guiding significance for engineering construction.