Effect of roadwheel load, driving speed, and track slip upon stress state in sandy soil under tracked vehicle loading

Stress states in sandy soil have been determined in a field experiment using a stress state transducer (SST). An SST was placed in soil so that the depth from the untrafficked soil surface to the top of the SST was 10 cm. The soil was trafficked by the right track of test vehicles. Three tracked vehicles with masses of 44.3, 12.13, and 12.83 Mg were used in the experiment in order to determine the effect of track loading. One of the test vehicles was driven at 5, 10 and 20 km/h over the SST to determine effects of driving speed. Moreover, another test vehicle was driven with 5, 20, 40, 60, 80, and 95% track slip to investigate if track slip affects soil stresses. The results of field experiments were compared with analytical predictions based on the Boussinesq theory and the Mean Maximum Pressure and Nominal Ground Pressure models. It was concluded that track load and driving speed affected soil stress state components. A comparison among measured and calculated stresses revealed that the models gave results within 40–60% of the measured soil stresses, with the MMP model giving the highest and the NGP the lowest values among the analytical results. This trend was valid for all three test vehicles.