Understanding aggregate effects within fault fracture zones is crucial for assessing fault reactivation risks in grouted deep coal mines. This study investigates the compressive-shear damage mechanisms of grouted concrete specimens with varying aggregate contents (20%, 40%, 60%) and particle sizes (1–5 mm, 6–10 mm). Uniaxial compressive-shear tests were monitored synchronously using digital image correlation (DIC) and acoustic emission (AE). Additionally, a calibrated PFC2D discrete element model, incorporating matrix, aggregate, and interfacial transition zones, elucidated the mesoscale mechanisms. Results indicate: (1) peak shear load decreases linearly ( R 2 >0.86) with increasing aggregate content, dropping 64.3% from 20% to 60%, driving a transition from brittle to plastic failure; (2) AE b -value evolution tracks progressive damage, while damage rate k exhibits contrasting size-dependent trends; (3) macroscopic failure modes are synergistically controlled by aggregate size and content; and (4) numerical simulations validate the mesoscale mechanical origins of this brittle-to-plastic transition. These findings reveal the micro-mechanical mechanisms of anisotropic failure and re-strengthening in grouted fault materials, offering vital geological insights into stress evolution and instability precursors during fault reactivation.
Feng et al. (Fri,) studied this question.