The influence of surface roughness form on the strength of sand–structure interfaces

Laboratory experiments performed on friction sleeves sheared against sands of varying particle angularity and size have shown the important role of surface texture on the strength of sand–material interfaces. This paper presents the first study that characterises the influence of surface roughness form on the shear response of sand–material interfaces. The results presented show that artefacts with periodic non-clogging surfaces (i.e. of structured roughness form) mobilise interface friction angles that readily reflect ‘δ > ϕ conditions’. On the other hand, artefacts with clogging-prone surfaces (i.e. of random or ribbed roughness form) mobilise interface friction angles that are restricted to ‘δ = ϕ conditions’. This difference is dictated by interface clogging. The surfaces of structured form avoid clogging and mobilise additional passive resistances during shear, as opposed to surfaces of random and ribbed form which clog and only mobilise sand–material or sand–sand friction. This observation is validated by means of post-shear sand deformation measurements. The findings presented in this paper can help in the design of geotechnical systems with enhanced load-carrying capacity.