Highlights • Soil shear strength measurement methods used in terramechanics studies. • Modelling of the terrain behaviour “Evaluation of the terrain” when subjected to an excitation load. • Influence of moisture content on the soil strength. • Loam sand soil shear strength results at different moisture contents using direct shear test. • Designs prepared by researchers for measuring the shear strength of the soil at higher shearing speed, thus suitable to terramechanics study case.

Abstract This article aims to give a background about the soil shear strength and its measurement methods based on scientific articles and the work of researchers. A brief introduction is given about terramechanics science and the loads acting at the interaction zone between the tractive element (wheel/track) and the terrain. The most important loads exciting the terrain from the machine’s tractive element are the normal and the tangential loads. The tangential load will shear the terrain/soil and might lead to slippage, thus it is important to study the shear strength of the soil. In the review the soil terrain behaviour as an elastic and a plastic region is discussed. The conventional methods for measuring the soil strength used by scientists in terramechanics studies are reviewed. The influence of moisture content on soil strength is also taken into consideration. New ideas created by terramechanics scientists that emulate a real wheel/track - terrain interaction case for measuring the soil shear strength and are not civil or geotechnical engineering methods are mentioned. Finally, the shear strength results of loam sand soil obtained using the direct shear test conducted at the Hungarian University of Agriculture and Life Sciences (MATE) are presented.