Several researchers have studied the behavior of particles during shearing to have better insight on the Mohr-Coulomb (MC) strength parameters. In most cases, the movements of particles along the shear band were studied by means of numerical modeling to obtain the velocities and directions of the soil particles. The use of a transparent shear box highlights the original enhancement and contribution in this paper to study the mechanical behavior of particles using particle image velocimetry (PIV) along the shear zone. Earlier literature on research utilizing "transparent shear box" consisted of several limitations such as obstructed view of the shear zone or using numerical simulation. The tested specimens consisted of sand and reconstituted rock spoils of metagreywacke and shale origins, which were classified according to their shapes and mineralogy contents. Particle shearing behavior were analyzed in detail at various stages throughout the direct shear tests with results complementing the PIV assessments. This novel interpretation technique has successfully demonstrated how particle shapes and angularity, mineralogy as well as effects of particle dilation and compression under shear, can influence the strength parameters.
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.
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