Determining and analysing the stress state under wheeled-vehicle loads

Abstract

This paper contains experimental data from the soil stress state under wheeled-vehicle loads obtained in several field experiments. Three-wheeled vehicles were used for the tests: a 14t 6×6 and a 6t 4×4 truck as well as a 3.1t agricultural tractor. The vehicles were driven over different types of soils (sandy soil, loess (clay), and turf) and over a snow cover. The measuring method is described. An analysis of principal stresses as well as octahedral stresses was performed taking into account the following factors: vehicle weight and wheel loading, vehicle speed, multiple passes, reduced inflation pressure, and wheel-function modes (rolling and driving). An analysis of octahedral stresses was performed on the basis of correlations between these stresses and the drawbar pull force generated by the vehicle. The most significant finding from this work is that the soil stress under a loaded vehicle depends not only upon the contact pressure but also upon factors that change during operations, such as the speed, wheel slip, load distribution, and multiple passes. This explains why the results of off-road mobility and trafficability models based on flat values of wheel—soil pressure may vary far more than expected. It was also concluded that soil stresses are affected by rolling and driving modes, but the relationships are different for sand and loess soil surfaces.