Coal gangue is a waste product commonly produced during coal mining. Using gangue as a replacement for conventional aggregates in shotcrete applied to underground roadways is a feasible approach to promote the resource utilization of gangue solid waste. The mix proportions of shotcrete materials are crucial to the effectiveness of field applications. The aim of this study was to investigate the effects of mix proportions on the mechanical properties of the gangue-based shotcrete material applied to roadways. To achieve this, we conducted experiments to measure changes in the slump under different gangue sizes, mass concentrations, sand contents, and cement contents. The study analyzed the influences of various mix proportions on the conveying and mechanical properties of the gangue-based shotcrete material applied to roadways. The slump and the compressive strength were analysed. The following was concluded: (1) The gangue size and sand content have a similar effect on the slump. As the gangue size and sand content increase, the slurry slump initially decreases and then increases, which is attributed to the plasticity of the aggregates themselves. The mass concentration has a negative correlation with the slump, which is the least sensitive to changes in cement content. (2) The compressive strength of all specimens increases with prolonged curing, reaching its maximum after 28 d under the compressive experimental conditions. (3) This paper analyzed the reasons for better mechanical properties under the conditions of smaller size gangue, higher mass concentration, and higher cement content. It has also examined the reasons for greater compressive strength at 35% sand content. The experimental results of this paper also offer relevant guidance regarding the specific mix proportions of the material of the field gangue-based shotcrete material applied to roadways.

The mechanical durability of gangue-based roadway shotcrete material (GRSM) in aqueous environments was systematically investigated by evaluating the effects of immersion duration, dry–wet cycles, and pH variations on its uniaxial compressive strength (UCS). The results indicate that prolonged immersion significantly degrades the mechanical performance of GRSM. After 28 days of immersion, the UCS decreased by 8.68 MPa (22%) compared with specimens under standard curing conditions. In contrast, limited dry–wet cycling (up to two cycles) enhanced the UCS to 36.05 MPa by promoting continued hydration and pore refinement, whereas additional cycling led to progressive deterioration. GRSM exhibited pronounced pH sensitivity: acidic environments induced the most severe strength loss, followed by alkaline conditions, whereas neutral to weakly alkaline environments (pH 8–12) resulted in relatively stable mechanical performance. Mercury intrusion porosimetry (MIP) confirmed that pore structure evolution governed strength variation, with acidic exposure and dry–wet cycles producing the greatest increases in porosity. Mechanically activated gangue (MA-gangue) was prepared by ball milling and partially substituted for cement. Although MA-GRSM exhibited lower UCS than conventional GRSM under all conditions, both materials demonstrated similar environmental response patterns. These findings elucidate the coupled physicochemical mechanisms governing the durability of gangue-based shotcrete materials in underground water-bearing environments.

To investigate the mechanical response and evolutionary mechanisms of shear-slip rockburst in fractured rock masses, intact, single-fracture, and double-fracture cubic specimens were fabricated using a self-developed synthetic material designed to reproduce pronounced elastic energy storage and rapid brittle failure. Shear-slip tests were conducted under normal stresses ranging from 0.9 to 3.6 MPa. The impact energy index, elastic energy index, and dynamic failure time of the material were 18.0, 9.2, and 140 ms, respectively. Shear stress, shear displacement, and normal displacement were monitored synchronously, while stress-drop events, shear-surface damage, and rock-powder mass were analyzed to clarify the controlling effects of normal stress and the fracture configuration. The results showed that, as the normal stress increased from 0.9 to 2.7 MPa, asperity interlocking along the shear surface was enhanced, resulting in overall increases in the peak and residual shear strengths and progressive suppression of dilation. At 3.6 MPa, all three specimen types exhibited pronounced stress drops, normal contraction, and complete loss of shear-bearing capacity, indicating a transition from stable frictional sliding to crushing collapse dominated brittle instability. The tested specimens suggest that increasing the number of prefabricated fractures may promote deformation localization and shorten the stable post-peak sliding process. At 3.6 MPa, the shear displacements corresponding to complete instability of the intact, single-fracture, and double-fracture specimens decreased from 9.0 to 7.8 and 6.5 mm, respectively, whereas the maximum stress drops increased from 0.28 to 0.62 and 0.90 MPa. These responses were characterized by earlier instability, increasingly concentrated stress-drop events, and larger individual stress drops. With increasing normal stress, the mass of rock powder increased from 11 to 56 g, indicating that shear surface damage evolved from localized fracturing to intensive crushing and grinding. The shear-slip process comprised four stages: compaction adjustment and load-bearing structure formation, elastic shearing and energy accumulation, damage accumulation and crack coalescence culminating in peak instability, and fragment reorganization with post-peak sliding. These findings provide experimental evidence for identifying shear-slip dynamic instability in fractured surrounding rock.