Designing explosion rated ventilation seals for coal mines using high-fidelity physics-based computer modelling
Questions have been raised about the effectiveness of ventilation control devices (VCDs) to safely resist explosions during their intended life. This functionality depends on the ability of the VCDs and in particular seals to withstand changes in the behaviour of the strata, particularly where longwall abutments influence the stress regime in and around the chain pillars. As a consequence of an explosion impact on a seal, the surrounding strata could experience increased loads possibly resulting in permanent deformation and requiring grout consolidation. These aspects of seal design have been investigated using advanced numerical analysis. Globally since the early 20th century, to protect underground personnel, ventilation seal designs have been required to be tested at an internationally recognized explosion test gallery to achieve pressure ratings required by legislation. The last two decades has seen advances in materials technology and engineering of structures. It has become accepted practice to use numerical methods to provide engineering ratings for mine seals in line with other industries where the elimination of prototype testing provides more rapid product introduction to the market. Before presenting the results of numerical analysis, structural aspects of seal design are simply explained including arching behaviour and the contribution of dynamic magnification due to impact loads. High-fidelity physics-based computer simulations using software LS-DYNA were able to predict the results from physical testing of mine based seals in a most realistic way. Test data from live gas/coal dust deflagration explosions at Lake Lynn, PA, USDA along with pressure-time curves recently developed by the National Institute of Occupational Safety and Health as a result of the study of explosive atmospheres, were used to simulate a realistic loading environment caused by 138 kPa (20- psi) and 345 kPa (50-psi) explosions in physics-based models of seals.