Measurements and simulations of rut depth due to single and multiple passes of a military vehicle on different soil types

Accurate prediction of rut depth caused by military vehicles trafficking is crucial for the success of their mission. In addition to the operational aspect of trafficability and mobility, military vehicle traffic can lead to severe degradation of soil functions. The objective of this study was (i) to examine rut depth formation and bulk density changes after one and repeated passages of a military vehicle on different soils and land uses, and (ii) to assess the ability of an analytical soil compaction model to predict these changes. The wheeling tests were carried out with a 7 Mg military truck at seven sites in Estonia covering soil textures from sand to clay and a peat soil. Rut depths and bulk density at various depths were measured after one and ten vehicle passes. Undisturbed soil samples were collected next to the tracks for determination of initial soil compressive properties used for parameterisation of the model. The smallest rut depths were measured on arable soils, both after one and ten vehicle passes. The largest rut depth after one pass was obtained on the peat soil, while the largest rut depths after ten passes were measured on the grassland soils. The model overestimated rut depths on the peat soil, and underestimated the increase in rut depth from the first to the tenth pass on the grassland soils, while predictions for the arable soils were adequate. We identify a need for studies on the mechanical behaviour of peat soils during wheeling and for better quantitative description of multi pass effects, especially on soft soils.