Behaviour of reconstituted sand-sized particles in direct shear tests using PIV technology

This paper presents a study on the mechanical behaviour of reconstituted tunnelling rock spoils carried out using direct shear test. The objective is to study the Mohr-Coulomb (MC) failure criteria of sand and sand-sized spoils of metagreywacke based on their respective particle shapes. Particle motions were tracked using Particle Image Velocimetry (PIV) technique. A remotely controlled camera was used to capture sequential images, which were then processed using GeoPIV to produce particle movement vectors. The captured vectors were analysed to detect notable sample behaviours such as dilation and contraction, as well as particle interlocking and breakage. It was found that factors affecting cohesion include: a) effect of particle shapes and surface roughness; b) effect of confining stress and c) effect of particle interlocking and breakages