Factors Affecting Bevameter Soil Characterization

The Bekker-Wong soil-wheel interaction model has been widely adopted in the terramechanics community. This approach requires data measured with a Bevameter. The Bevameter test includes a pressure-sinkage test and a shear strength test. Although the original intention of the Bevameter method is to closely replicate the interaction between the wheel/track and the soil, tests are often done at lower vertical loads with smaller contact areas to keep tests within practical experimental limits. The traditional Bevameter shear strength test, which uses a rotational shear ring with grousers, tends to overpredict the drawbar pull of vehicles by 30 to 40% [(Chang and Baker, 1973, Shoop, 1993)]. Translational shear arguably more closely resembles the shear mechanism that occurs between a wheel/track and the soil. The literature indicates that terramechanics investigations are significantly influenced by soil condition and preparation. This study investigates (a) the influence of soil preparation on the pressure-sinkage and shear-displacement relationship of sandy soil, (b) the influence of the shearing mechanism on shear strength, and (c) the influence of shear contact area on shear strength. Experimental results indicate that soil preparation has a substantial influence on the pressure-sinkage relationship. The shearing mechanism was investigated by comparing traditional rotational shear with translational shear. The findings indicate that the shearing mechanism may explain the overprediction of shear strength typical of rotational shear tests. The shear contact area also exhibits a significant influence on the measured shear strength. Further investigation into the shear mechanism and size and shape of the shear contact area is recommended.