Micromechanics-Based Strength Criterion for Root-Reinforced Soil

To address the limitation of using experimental parameters in the macroscopic strength criterion, a micromechanical strength criterion for root-reinforced soil is developed. In this model, a micromechanical model for a three-phase composite (“root—cemented soil matrix—frictional element”) is constructed, and the novel combination of energy equivalence principles with the M-T method is used to determine the meso-scale prestress and strength criterion for root-reinforced soil under freeze–thaw cycles. The representative volume element (RVE) of root-reinforced soil is conceptualized as a composite material consisting of a bonded element (a cemented-soil matrix with root inclusions) and frictional inclusions. By applying micromechanics, along with the Mori–Tanaka method, the LCC method, limit analysis theory, and macro–micro energy equivalence principles (incorporating both strain and dissipated energy), a micromechanical strength criterion is formulated, revealing failure mechanisms at the microscale. The previously used stepwise procedure for deriving the stationary function is improved, and the microscale prestress is determined through the Mori–Tanaka method combined with macro–micro strain-energy equivalence. The proposed micromechanical strength criterion effectively models the primary strength variation in root-reinforced soil under freeze–thaw cycles, extending the existing shear criterion for soil.