Comprehensive enhancement of blasting performance and dust suppression in open-pit mines using a modified mudstone–fly ash geopolymer stemming material

In response to the severe dust pollution, high operational cost, and short-lived effectiveness associated with conventional water-spraying dust suppression in large open-pit coal mines in grassland regions, this study proposes a source-control strategy grounded in solid waste reutilization. Drill cuttings of mudstone obtained from a representative overburden bench in the study area were utilized as the primary precursor, and a modified mudstone-fly ash geopolymer stemming material was developed via an alkali-activated rapid-setting process. The proposed material enables synergistic optimization of explosive energy confinement and dust suppression at the source during blasting operations.The dust-suppression mechanism of the proposed material was systematically investigated through mechanical performance testing, SEM, XRD, EDS, and smoothed particle hydrodynamics (SPH) simulations.Results show that optimal performance is obtained with a 30% accelerator concentration, a water-glass modulus of 1.50 mol/L at 40 g/L dosage, and a mixing time of 5 min, yielding good flowability and setting times within 30 min. Dynamic tests indicate superior toughness, with initiation and propagation fracture toughness of 0.80-2.41 MPa m^1/2 and 0.61-2.56 MPa m^1/2, respectively, and a peak stress approximately 7.5% higher than that of in-situ mudstone. Microstructural analyses reveal that synergistic formation of C-S-H and C-A-S-H gels produces a dense and stable matrix.SPH simulations identify an optimal stemming length of 2.5 m for uniform energy distribution. Field trials demonstrate reductions of 40.0% in peak dust concentration and 0.346 cm/s in maximum vibration velocity, alongside improved fragmentation and suppressed blowout holes. The results demonstrate that the proposed geopolymer stemming material enables a technological transition from conventional post-blast water spraying to in-blast active solidification control. By enhancing explosive energy utilization while achieving source-level dust suppression, the material provides a green, cost-effective, and durable solution for blasting optimization in grassland open-pit coal mines.