Alvin C. Bailey

A Stress State Transducer for Soil

ABSTRACT Atransducer was developed that measured normal pressures in six predetermined directions to provide data for mathematically determining the complete stress state in soil. The stress state transducer was evaluated under hydrostatic loading in both a sand and a clay. All six sensing elements registered within 6% of the applied pressure.

A Soil Compaction Model for Cylindrical Stress States

ABSTRACT Asoil compaction model that includes soil behavior under compressive normal and shearing stresses great enough to attain maximum compaction was developed. The model was developed and verified with triaxial tests on several agricultural soils. This model predicts soil compaction under vehicle loads better than earlier models because the input stress state can more realistically represent field conditions.

A machine for testing tractor tires in soil bins.

ABSTRACT THE National Tillage Machinery Laboratory (NTML) single-wheel tester has been redesigned to increase the tire-size capability and to provide electro-hydraulic servo control of the forward and angular velocities of the test wheel and the vertical load on the test wheel. This paper describes the operation and capabilities of the redesigned tire tester.

Soil Stress State Determination Under Wheel Loads

ABSTRACT TWO 6-directional stress state transducers were used to measure soil stresses beneath a moving tire in the soil bins at the National Soil Dynamics Laboratory. Principal stresses, stress invariants, and octahedral normal and shearing stresses were calculated from the measured stresses. The ratio of octahedral shearing to octahedral normal stress indicated high shearing action under the tire although the tire was developing no net traction.

Effect of total load on subsurface soil compaction.

ABSTRACT TWO different size tires carrying unequal total loads that resulted in approximately equal soil surface pressures were run over soil pressure transducers buried at 18-, 30-, and 50-cm depths. The larger tire consistent-ly produced higher soil pressures at these depths. Froehlichs equation approximately described the soil pressure distribution in both a sandy soil and a clay soil with uniform density profiles. However, when a com-pacted layer was inserted in the density profile, this equation was no longer suitable. The data indicated no simple relationship between soil pressures and bulk densities.

Multipass Behavior of a Pneumatic Tire in Tilled Soils

ABSTRACT A13.6 X 38 tractor tire was operated at the recom-mended load of 16.3 kN and also at half load to simulate dualing. The tire was run four times in the same rut in three different soils. Each soil was freshly tilled and loose before the first pass. Results showed both net traction and tractive efficien-cy significantly lower on the first pass than on subse-quent passes. Sinkage and bulk density changes were noted after each of the four passes. Approximately 75 percent of the total change in bulk density and 90 per-cent of the sinkage occurred on the first pass of the tire.

Radial Tire Performance in Firm and Soft Soils

ABSTRACT ARADIAL ply tire and a bias ply tire were compared in both soft and firm soil conditions. The coefficient of net traction and the tractive efficiency were consistently higher for the radial ply tire in five of seven soil conditions. There was essentially no difference in the performance of the two tires in the other two soil condi-tions. The advantage for the radial ply tire was greatest in the firm soils.

Determining Components of Soil-Metal Sliding Resistance

ABSTRACT An experimental technique and method of analysis for determining the adhesive and frictional components of the sliding resistance between soil and another material were developed and tested. By controlling the loading history of the sliding interface, the effects of nor-mal stress and initial sliding-path length on the adhesive component were determined. Normal stress and sliding-path length affected the adhesive component greatly but had very little effect on the frictional component.

Shear Measurement for Agricultural Soils — A Review

ABSTRACT SHEAR measurement methods and devices are reviewed and compared. Problems associated with shear measurement are identified and recommendations are given.

Soil Compaction by Continuous Deviatoric Stress

ABSTRACT Ahydrostatic compaction model for unsaturated soils was expanded to include continuously increasing deviatoric stress. The expanded compaction model was developed and evaluated using two types of load paths on triaxial test samples from four agricultural soils. The model satisfied the boundary conditions at low and high stress levels and predicted soil bulk density within 4 percent of measured bulk density.