The study of deformable soils is one of the key factors in determining the tire, vehicle and/or agricultural tool design parameters. This literature review provides a brief overview of soil classification, soil testing, soil constitutive models, and numerical approaches utilized to model soil-tire/tool interaction. In the past, empirical, semi-empirical, and analytical soil models were used in these studies. However, some limitations occurred in terms of characterization of soil-tire/tool interaction in detail due to a large number of variables such as cohesion, moisture content, etc. In the last few decades, the finite element (FE) method was used with different formulations such as Lagrangian, Eulerian, and Arbitrary Lagrangian Eulerian to simulate the soil-tire/tool interaction. Recently, particle-based methods based on continuum mechanics and discrete mechanics started to be employed and showed good capability in terms of modeling of soil deformation and separation. Overall, this literature review provides simulation researchers insights into soil interaction modeling with tires and agricultural tools.(c) 2023 ISTVS. Published by Elsevier Ltd. All rights reserved.

For the characterization of soil stiffness anisotropy at small strains and the calculation of soil elastic constants derived from the cross-anisotropic model, it is important to obtain stress wave phase velocities of soils in both principal and oblique directions. This study developed an original eight-prismatic shape apparatus equipped with disk-shaped shear plates to measure shear (S-) wave phase velocities (V-phase) in multiple directions, and four granular materials of various shapes were tested by this apparatus under isotropic confinement. Experimental results confirm the capability of the new apparatus and reveal that both S-wave propagation and oscillation directions are sensitive to soil inner fabric, i.e., V-s changes with the variation of either S-wave propagation or oscillation direction. Based on the experimental observations, it is suggested to keep the same S-wave oscillation direction when measuring V-s in multiple propagation directions so that the corresponding shape of the S-wave surface (polar plots of V-s in arbitrary propagation directions) is more precise to reflect the small-strain stiffness anisotropy of soils.