Experimental analysis and risk assessment of projectiles expelled from mine openings due to underground coal mine explosions

The safety of personnel working in coal mines is a critical concern that necessitates a comprehensive understanding of explosion dynamics, mining operations, and safety protocols. While there is a considerable body of knowledge about gas emissions and gas/coal dust explosions in underground mines, little attention has been paid to the potential risks associated with explosive forces and projectiles expelled through mine openings. Such hazards can result in injuries and fatalities to personnel underground and at the mine portal, as well as catastrophic damage to infrastructure in the vicinity of the mine opening on the surface. Previously, the authors successfully developed a methodology for prescribing exclusion zones around mine entrances against blast wave hazards (Remennikov and Gan, 2023a, Gan and Remennikov, 2024). To address projectile hazards, the authors employed the methodology from the NATO manual AASTP-1 (2023) which was intended for ammunition storage and applied in the context of mining in the interim. For this project, the previous work is expanded to produce new data from innovative test setups that closely replicate the conditions of underground coal mine drifts. For the first time, the effect of the angle of drift inclination on projectile hazard safety distances is studied experimentally as it is anticipated that larger angles of mine drift inclination could make the projectile range more severe. The proposed methodology is based on establishing a relationship between the parameters of blast waves around a mine opening (e.g., peak static and dynamic overpressure, impulse, etc), characteristics of objects (e.g., geometry, drag coefficient, mass, size, etc), an incline of drift, and the resulting behaviour of the projectiles (e.g., initial velocity, flight trajectory, maximum travel distance, etc). An Advanced Blast Simulator (ABS) with cross-sectional dimensions of 0.3 m x 0.3 m is employed for this study to conduct a series of gas explosion experiments simulating blast waves and projectiles expelling from a mine portal entry and over the mine surface. Projectiles representing geometrically scaled mining objects and generic shapes of various sizes and masses are considered. The outcome of this project will support the development of exclusion zones around mine entries to prevent infrastructure damage and personnel injury due to blast wave and projectile hazards.