Thermo-hydro-mechanical coupling effects on cyclic dynamic behavior of saturated soft soil

Cyclic thermo-hydro-mechanical (THM) behavior of saturated soft soils remains insufficiently quantified, particularly regarding long-term deformation mechanisms. Temperature-controlled dynamic triaxial tests were systematically performed to evaluate thermo-mechanical responses in saturated soft soils. Results revealed that cumulative plastic strain exhibited a linear negative correlation with temperature, decreasing by 0.013% per 1 °C rise within the 20 °C-40 °C range. A multifactor-coupled predictive model for cumulative plastic strain was established based on temperature effects and critical parameter thresholds, accompanied by optimization strategies for soft soil. Elevated temperature suppressed pore pressure through dual pathways: enhanced consolidation drainage and thermal effective stress generation, leading to decreased initial growth rate and stabilized pressure. This suppression exhibited threshold-governed nonlinearity at critical confining pressure and dynamic deviator stress. The thermal efficacy diminished under low confining pressure due to increased soil expansion freedom or under high dynamic deviator stress due to accelerated cementation structure damage. The enhancement of dynamic plastic modulus exhibited confinement characteristics beyond the static deviator stress threshold, with pre-existing particle interface damage mechanistically attenuating thermal-induced modulus enhancement. These findings provide theoretical and experimental foundations for enhancing the long-term stability of soft soil foundations in thermally fluctuating environments.