Experimental Investigation of Factors that Influence Bevameter Terrain Characterisation

Abstract

The Bekker‐Wong soil‐wheel interaction model has been widely adopted in the terramechanics field. This model traditionally requires the soil to be characterised using a Bevameter, which entails performing in situ plate sinkage and shear stress tests. Bevameter soil characterisation is not a standardised test procedure, and the test setup may influence the identified soil model parameters. This study investigates the influence of the following five factors for partially saturated sandy soil: i) soil preparation on pressure‐sinkage, ii) soil preparation on shear stress, iii) torsional vs. translational shear mechanism, iv) shear contact area, and v) shear velocity. Literature indicates in situ soil mechanical properties exhibit stochastic behaviour; however, the uncertainty of the identified soil parameters is rarely taken into consideration. This study employs the Bayesian statistical framework for probabilistic parameter estimation and formal hypothesis testing. The results indicated that the influence of soil preparation on pressure‐sinkage response is substantial, exhibiting an order o magnitude influence. The influence of soil preparation on shear tests is notable, but less significant. The shear mechanism, shear contact area and shear velocity all exhibited a statistically significant influence (Bayes Factor >10) with a maximum absolute shear stress difference of 18%, 20% and 10%, respectively. Moreover, depending on the test setup configuration and data processing decisions, the estimated internal soil friction angles ranged from 16.5 to 37.5 degrees for the same soil. The findings are expected to have significant implications for the prediction of vehicle drawbar pull using the Bekker‐Wong model. Further investigation into which Bevameter test configuration is more representative of the shear stress‐displacement curve of an actual wheel is recommended.