HEAVY LOAD, LOW TIRE PRESSURE RUTTING OF UNBOUND GRANULAR PAVEMENTS

In a study of effects of wheels with very heavy loads but very low tir e inflation pressures on unbound, single-layer granular pavements, tra fficking tests were carried out on full-scale indoor pavements at the Pavement Test Facility, Transport Research Laboratory, Crowthorne, U.K . Two values of wheel load, two values of tire inflation pressure, and three subbase thicknesses were used. Testing was continued to 10,000 passes and a total of 4,704 measurements of rut depth made at interval s, providing a statistically significant data set. The development of ruts, the rut cross sections, and the effects of halving the tire infl ation pressure or nearly doubling the wheel load ate presented. Compar isons are made to a rut prediction equation derived by the U.S. Army C orps of Engineers Waterways Experiment Station in similar work, and co nclusions are drawn.