COMPACTION OF AN EARTHY SAND BY RUBBER TRACKED AND TIRED VEHICLES

Normal stresses exerted by two agricultural vehicles (a rubber tracked Caterpillar Challenger 65 and a Steiger Tiger 550 4WD tractor fitted with low pressure dual wheels) were measured with electronic earth pressure cells at four depths (150, 300, 400 and 500 mm) in a sandy soil located in the West Australian wheatbelt. Cone penetration resistance and dry bulk density were also measured at these depths before and after traffic treatments. Uniaxial soil compression testing was done on soil cores sampled at the 300 mm depth where the peak normal stresses were measured during vehicle passage. The Cat 65 exerted less normal stress on the soil than the Steiger 550 at 400 and 500 mm depth. However, the soil had a higher penetration resistance after the passage of the Cat 65 relative to the Steiger 550. Profiles of cone penetration resistance were more discriminating in distinguishing soil physical changes among the trafficked and untrafficked treatments than dry bulk density and most of the parameters derived from compression tests.