PREDICTION OF ASPECTS OF SOIL WHEEL SYSTEMS

A simple formula is given which predicts maximum stress-depth relationships under wheels from vertical wheel load and the tyre inflation pressure. Predictions were compared with stress measurements at a depth of 30 cm under a wide range of vehicles, for zero rut depth, non-significant horizontal wheel force, and soil top layers overlaying more rigid subsoil. A very wide diagonal rubber tyre and a very wide radial polyurethane tyre were compared with respect to their contact stress distributions. Stress measurements at a depth of 15 cm showed that the former tyre produced higher peak stresses. If values of soil cohesion and angle of internal friction are available, the model SOCOMO can predict size and location of plastic regions in soil under tyres. If only specific types of field traffic and given pieces of land are considered, it is possible to measure useful relationships between soil water content at traffic event and traffic-induced change of any soil physical property.