Water-sand mixture inrush in underground pathways: Risk factors and mitigation strategies

Water-sand mixture inrush (WSMI) events pose severe threats to mining safety, infrastructure stability, and subsurface operations. This study first develops a pathway loss model to integrating frictional and expansion-induced hydraulic head losses, and then applies the Sobol-based global sensitivity analysis (GSA) to the model to evaluate WSMI risk for the following two scenarios (1) direct pathway-induced WSMI (with short, gravity-driven pathways) and (2) indirect or combined pathway-induced WSMI (with long, complex, pressure-driven pathways). For the two scenarios, GSA identifies fluid velocity as the dominant parameter, with pathway expansion loss governing direct inrush and friction loss dominating indirect inrush. Hydraulic head loss is markedly higher in the indirect inrush scenario than in the direct inrush scenario. Accordingly, tailored mitigation strategies are developed. For the direct inrush scenario (simple pathways), the priority is to cut off the energy conversion chain; for indirect inrush scenario (complex pathways), the focus is on dissipating excess energy. These findings advance the mechanistic understanding of WSMI and offer scenario-specific guidance for hazard control.