Chapter 5 - Characterization of the Shearing Behaviour of Terrains

Abstract

This chapter describes the results of the measurement and characterization of the shearing behavior of a variety of terrains, including mineral terrain, muskeg, and snow-covered terrain. The measurements are made using a vehicle-mounted bevameter with the associated computerized data acquisition and processing system. When a multiaxle wheeled vehicle (or a tracked vehicle) is in straight-line motion over an unprepared terrain, an element of the terrain is subject to the repetitive shearing of the consecutive wheels (or roadwheels). In order to predict the shear stress distribution on the vehicle–terrain interface, the response to repetitive shear loading of the terrain should be known. The response of a frictional terrain (a dry sand) to repetitive shear loading under a constant normal load indicates that when the shear loading is reduced to zero and is then reapplied, the shear stress–displacement relationship during reshearing is similar to that when the terrain is being sheared in its virgin state. The variation of the shearing force beneath a rectangular shear plate on dry sand subject to a vertical harmonic load with a frequency of 10.3 Hz indicates that during the loading portion of each cycle, the shearing force S does not reach its maximum value instantaneously.