Underground » Ventilation, Gas Drainage and Monitoring
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 exit, as well as catastrophic damage to infrastructure in the vicinity of the mine opening on the surface.
In research component 1 a methodology for prescribing exclusion zones around mine entrances against blast wave hazards (Remennikov & Gan 2023) was successfully developed. To address projectile hazards, the authors adopted 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 research component 2, the work was expanded to use innovative test setups that closely replicate the conditions of underground coal mines. New experimental and computational data were generated to capture coal mine specific explosion scenarios, including the characteristics of gas explosions, the influence of drift inclination, shaft orientation on projectile flight paths, and typical coal mining objects.
An Advanced Blast Simulator (ABS) with cross-sectional dimensions of 0.3 m x 0.3 m was employed for this project to conduct a series of gas explosion experiments simulating blast waves and projectiles expelling from mine exits (portals, shafts and boreholes) and over the mine surface. The extensive experimental program provided insights into the effects of blast parameters, object characteristics, and drift incline on launch velocity, launch angle, and range of typical coal mining objects. Experimental testing showed that end jets are generally narrow and travel along the tunnel axis, with projectiles generally following the jet stream unless they interact or collide with another slow-moving object, where they could be redirected. Additionally, projectiles from shafts or boreholes typically do not exceed the 33° of pitch angle.
The proposed methodology to define exclusion zones was characterised by projectile risk categories driven by methane-air volumes nominated for a representative mine geometry. CFD simulations of these mine scenarios were used to generate realistic blast jet loads and dynamic pressures at mine exits. An in-house computer code, which considers blast physics, flight mechanics, and projectile motion equations was developed to compute their maximum hazardous ranges for typical coal mining objects.
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.