The size effect of pressure-relief roadway on coal-gas outburst dynamics

Coal-gas outburst accidents typically exhibit distinct characteristics in terms of outburst hole and roadway behaviors. In outburst experiments, the different size devices are developed to simulate outbursts. Thus, a key question arises: what specific dynamic impacts do the size and shape of pressure-relief roadways exert? With the difined parameter of pressure potential energy release rate (PPERR), the size effect of the roadway on the outburst two-phase flow dynamics is explored by changing its caliber, cross-sectional area, length, shape, similarity ratio and relative position to outburst holes. The results indicate that small-caliber roadways and low roadway heights impede the release of outburst energy and induce fluctuations in energy release. The direct release without roadway makes PPERR increased by 5.62%, and it is inconsistent with the constraints of the roadway in outburst accidents. In roadways of different shapes, the two-phase flow velocity is the same with the same cross-sectional area and different in PPERR: square > rectangular > circular. The use of a cross-cut parallel to the coal seam (90°) to uncover coal produces the least outburst dynamic and the smallest rate of energy release. The increase of similarity ratio will cause the linear growth of PPERR, but has no effect on the velocity of outburst two-phase flows, and the similarity ratio should not be lower than 0.1. These findings hold practical guiding significance for optimizing roadway size design and formulating roadway excavation schemes in mining engineering, thereby contributing to the mitigation of outburst dynamic effects. Coal-gas outburst accidents typically exhibit distinct characteristics in terms of outburst hole and roadway behaviors. In outburst experiments, the different size devices are developed to simulate outbursts. Thus, a key question arises: what specific dynamic impacts do the size and shape of pressure-relief roadways exert? With the difined parameter of pressure potential energy release rate (PPERR), the size effect of the roadway on the outburst two-phase flow dynamics is explored by changing its caliber, cross-sectional area, length, shape, similarity ratio and relative position to outburst holes. The results indicate that small-caliber roadways and low roadway heights impede the release of outburst energy and induce fluctuations in energy release. The direct release without roadway makes PPERR increased by 5.62%, and it is inconsistent with the constraints of the roadway in outburst accidents. In roadways of different shapes, the two-phase flow velocity is the same with the same cross-sectional area and different in PPERR: square > rectangular > circular. The use of a cross-cut parallel to the coal seam (90°) to uncover coal produces the least outburst dynamic and the smallest rate of energy release. The increase of similarity ratio will cause the linear growth of PPERR, but has no effect on the velocity of outburst two-phase flows. These findings hold practical guiding significance for optimizing roadway size design and formulating roadway excavation schemes in mining engineering, thereby contributing to the mitigation of outburst dynamic effects.