An Experimental Investigation on the Tribological Behaviour of Nominally Flat Quartz Grains with Gouge Material in Dry, Partial Saturated and Submersed Conditions

We examined the normal and tangential contact behaviour of gouge materials between nominally flat quartz grains using micromechanical experiments. Primary mixtures of plastic clay (montmorillonite) and non-plastic silt (crushed aggregates) were used as gouges to focus the investigation on the tribological behaviour of gouge materials at dry, partial saturation and submersion conditions. The presence of gouges resulted in a decreased normal stiffness and frictional strength compared to pure quartz surfaces, and complex crushing behaviour. From cyclic shearing tests, montmorillonite showed the lowest secant stiffness and maximum energy losses, which were more pronounced at lower normal loads. Montmorillonite in its plastic and semi-solid states indicated that variation of post-peak softening and friction coefficient depend on the normal load at a given partial saturation level. In the sudden submersion simulation tests, both before and after the start of shearing, montmorillonite showed a significant decrease in the coefficient of friction (compared to dry gouge), unlike non-plastic silt.