Effect of cementation on the mechanical response of sands using acoustic emission technique

This study investigates the impact of cementation on the mechanical behaviour of sands with various cement contents (CSR – weight of cement relative to the total dry weight of the soil–cement mixture) in drained triaxial compression, employing both acoustic emission (AE) and environmental scanning electron microscopy measurements. The experimental findings, encompassing quantitative statistics of stress–strain relations, microstructural variations and AE characteristics, demonstrate that the addition of CSR from 1% to 20% leads to an exponential rise in peak strength and stiffness, marking a transition from ductile to brittle mechanical failure, which is pinpointed between the CSR levels of 5% to 10%. AE characteristics unveil an upward-opening parabola of normalised AE hits with CSR, a clear transition zone identification and three distinct types of AE rate evolutions corresponding to failure patterns of ductile bulging, shear banding and brittle fracturing, respectively. This suggests an intimate correlation with the intrinsic differences in micromechanical behaviours and AE propagation properties of cemented sands with varying CSRs. Notably, the bulging and shear banding processes are divided by AE into three stages, whereas fracturing is characterised into five stages. Two precursory AE anomalies associated with incipient failure and complex failure modes are observed, emphasising the advantage of using AE to reflect the internal micromechanical behaviour of cemented sands over conventional stress–strain manifestations.