A. Javadi - ۱.Iranian Agricultural Engineering Research Institute, P. O. Box: ۳۱۵۸۵-۸۴۵, Karaj, Islamic Republic of Iran.
G. Spoor - Cranfield University , Silsoe College, Bedfordshire, MK۴۵ ۴DT, U.K.,

This research explores the possible benefits to be derived from interactions between wheels, for supporting a greater proportion of applied loads in the shallower soil layers. This creates possibilities for reducing the risk of deep soil compaction. Previous research indicated that different interaction modes occurred under simulated wheel arrangements, being mostly dependent upon the spacing between them. Hence, field experiments were arranged to investigate a range of spacings between dual wheels in practical situations. Two field conditions were prepared providing loose and firm surface layers. Dry bulk density, penetration resistance, wheel sinkage and contact area were measured under each arrangement. A clear link was identified between results previously obtained in soil bin tests and those in the field, confirming that spacing has a major effect on the potential benefits. As wheel spacing decreased the interaction increased, inducing a greater resis-tance in the soil surface layers to carry higher loads. The optimum range of appropriate spacings and interaction modes identified in the laboratory tests was found to be applica-ble in the field.

Compaction, Load support, Wheels, Wheel spacing