Modelling the thermo-mechanical behavior of saturated fine-grained soils

This paper presents a simple thermo-elasto-plastic constitutive model for saturated fine-grained soils, addressing thermal volume change, excess pore pressure, and shear strength. The model incorporates a novel temperature-dependent plastic modulus formulation that attributes the thermoplastic strain to an internal state variable representing the thermal stabilization of soils due to cyclic thermal loading. It can capture the accumulative volume expansion of highly overconsolidated (OC) soils, and the accumulative contraction of normally consolidated (NC) and slight OC soils after several heating–cooling cycles. A thermally induced pore pressure formula is derived with consideration of thermo-elastic expansion of pore water and soil particles, thermo-plasticity of soil skeleton as well as the elastic unloading due to the decrease of effective stress under undrained heating. The effect of temperature on the shear strength was emphasized. An insight into the evolution of shear strength with temperature is provided. The consolidated stress history and stress path play a vital role in the thermal effect on the shear strength. The proposed model comprises nine parameters, which can be easily calibrated by element tests (triaxial tests and oedometer tests). The adequacy of the proposed model has been verified with experimental results from fine-grained soils documented in the literature.