Numerical analysis of tire mobility on deformable plastic clay in saturated conditions using total and effective stress frameworks

Modeling and performance prediction of tires on wet, plastic, cohesive soils is challenging. In wet soils, the undrained shear strength reduces as water content increases. This work aims to model highly deformable saturated clay (plastic state) to predict the short-term effect on the soil due to a single pneumatic tire pass. The external loads on the soil (total stresses) can be carried by the soil skeleton (effective stress) and/or water (pore water pressure). Fundamentally, effective stresses determine soil failure. Hence, material models can be defined using two frameworks: total and effective stress. In total stress analysis, commonly found in literature, soil and water are modeled as one medium to address rapid loading. In effective stress analysis, pore pressure evolution can be tracked through hydromechanical formulations with different drainage conditions (dry and fully saturated soils). Further, different numerical techniques (FEM, ALE, and SPH) are compared. The effective stress model captures an accumulation of excess pore water pressure after one tire pass resulting from soil non-linear behavior, which may potentially affect the tire performance of later passes. In addition, the FEM model fails at higher normal loads and slip ratios due to excessive deformation; ALE and SPH give more stable solutions for large deformations.¹