Hypoplastic modelling of thermo-mechanical behavior of root-reinforced soils

Global warming and the increasing frequency of extreme heat events pose significant challenges to the stability of vegetation-stabilized slopes. The mechanisms by which temperature variation influences the mechanical properties of root-reinforced soil remain insufficiently understood. This study developed a thermo-mechanically coupled hypoplastic constitutive model that incorporated root reinforcement mechanisms. To comprehensively verify model reliability, temperature-controlled consolidated undrained triaxial tests were conducted on root-reinforced soil. The experimental program considered multiple root contents over a temperature range from 20°C to 60°C. Additional experimental data reported in the literature were also adopted for external validation. Experimental results show pronounced thermal softening at elevated temperatures. The ultimate shear strength at 60°C decreased by approximately 29.4% compared with 20°C conditions. Despite this reduction, root reinforcement maintained relatively high absolute soil strength under high-temperature conditions. Comparisons between model predictions and both experimental results from this study and published data demonstrated the reliability of the proposed model. Furthermore, parameter sensitivity analysis revealed that strength enhancement exhibits diminishing marginal gains with increasing root content, indicating the existence of an optimal root content ratio. This study investigates the thermo-mechanical coupling mechanism of root-reinforced soil and provides tools for engineering design under extreme climatic conditions.