Uniaxial compaction of sand using 4D X-ray tomography: The effect of mineralogy on grain-scale compaction mechanisms

The mechanical behaviour of sand aggregates is often studied as a proxy for poorly consolidated sands and highly porous sandstones. Only recently research aimed at understanding deformation has started to use techniques that allow direct observation the in-situ grain-scale processes. Using state-of-the-art, time-lapse micro X-ray computed tomography (micro-XCT) imaging, influence mineralogy on compaction been investigated by performing uniaxial experiments four different mineral assemblies (quartz, K-feldspar, quartz + K-feldspar clay) room temperature dry conditions. For experiments, bespoke device (sample diameter 2 mm) was constructed coupled with micro-XCT imaging. This enabled strain-accommodating processes during deformation. To verify microstructural evolution observed in small-scale representative larger aggregate behaviour, conventional, centimetre-sized, control were performed. inelastic mainly accommodated such intragranular cracking intergranular sliding. At low axial stresses (10 MPa), grain fracturing occurred grains, if present, along cleavage planes. higher stresses, also observed. Presence clays, pores contacts, delayed onset breakage enhanced porosity reduction clay contacts facilitated sliding rearrangement.