A QUALITATIVE APPROACH TO THE PNEUMATIC TIRE-SOFT SOIL SYSTEM.
Final rept. Jun-Sep 66,
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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This study was directed toward obtaining a fundamental understanding of the tire-soil system from a qualitative investigation of the behavior of pneumatic tires operating in soft soils, using failure theories of classical soil mechanics. A series of powered-wheel, programmed-slip performance tests conducted in sand and clay were analyzed. The soil in contact with the tire is considered to be in a state of failure at all slips, and it is hypothesized that the characteristic shape of the pull-slip curve is not due to the increase in soil deformation, but to the rotation of the failure plane with respect to the tire-soil interface. Using some simple assumptions and the approximation that measured forces were uniformly distributed over the tire-soil contact surface, it is demonstrated that the hypothesis is a plausible one. A key element in the analysis is the determination of an angle theta that represents the angle of the tire contact surface relative to the horizontal. Using this angle and the forces measured in a test, a relation between the ratio of tangential and normal stresses and slip was developed. This relation is interpreted as a measure of the rotation of the failure plane. There appears to be a linear relation between theta and slip in sand, and a hyperbolic relation in clay. A discussion of slip is included as Appendix A. Author
- Soil Mechanics
- Surface Transportation and Equipment