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The study of airflow patterns at the ends of dead-end mine workings is crucial for optimizing underground mining ventilation systems. Understanding these patterns forms the basis for designing and implementing effective ventilation strategies.Previous studies have shed light on the behavior of the main vortex and the formation of stagnant zones in such environments, but these insights remain fragmented and call for a more systematic exploration to integrate them into a comprehensive theory.This paper presents the results of a thorough field investigation into the forced ventilation behavior in a dead-end mine working with a significant cross-sectional area (29.2 m2). We evaluated the impact of varying the setback distance of the ventilation duct’s end from the working face at intervals of 10, 15, 17, 19, and 21 m. The experimental design included precise measurements of turbulent airflow velocities at 25 carefully chosen points (in a 5x5 grid) for each setback distance, covering the area from the working face to beyond the end of the ventilation duct. This included additional measurements taken 1 meter and 10 meters past the termination of the ventilation duct, moving towards the entrance of the working area.The fieldwork was carried out in a typical dead-end stope at the Kupol gold-silver mine in the Chukotka Autonomous District, created by drilling and blasting.The volume of fresh air delivered to the working was maintained at a consistent rate of 17.4 m3/s across all scenarios, aligning with the mine’s standard air flow rate derived from the ventilation requirement for exhaust gases emitted by internal combustion engines of Load-Haul-Dump (LHD) machinery. With the duct’s terminal cross-sectional area at 0.8 m², this resulted in an inflow velocity averaging 21.75 m/s.Additionally, we included insights from three-dimensional numerical simulations performed in ANSYS Fluent, focusing on steady-state air movement and developed turbulence within the dead-end space. A comparative review of both empirical and modeled data shows that the ventilation jet, for all tested setback distances up to 21 m, successfully delivered air to the working face, where it then dispersed and initiated reverse flow patterns.These experiments led to the formulation of a linear relationship between the maximum relative velocity (compared to the initial jet velocity) at a distance of 1 m from the working face and a key geometric factor of the ventilation setup. This factor is the ratio of the duct’s setback distance to a characteristic dimension of the cross-sectional area, calculated as the square root of the cross-sectional area.
The study of airflow patterns at the ends of dead-end mine workings is crucial for optimizing underground mining ventilation systems. Understanding these patterns forms the basis for designing and implementing effective ventilation strategies.Previous studies have shed light on the behavior of the main vortex and the formation of stagnant zones in such environments, but these insights remain fragmented and call for a more systematic exploration to integrate them into a comprehensive theory.This paper presents the results of a thorough field investigation into the forced ventilation behavior in a dead-end mine working with a significant cross-sectional area (29.2 m2). We evaluated the impact of varying the setback distance of the ventilation duct’s end from the working face at intervals of 10, 15, 17, 19, and 21 m. The experimental design included precise measurements of turbulent airflow velocities at 25 carefully chosen points (in a 5x5 grid) for each setback distance, covering the area from the working face to beyond the end of the ventilation duct. This included additional measurements taken 1 meter and 10 meters past the termination of the ventilation duct, moving towards the entrance of the working area.The fieldwork was carried out in a typical dead-end stope at the Kupol gold-silver mine in the Chukotka Autonomous District, created by drilling and blasting.The volume of fresh air delivered to the working was maintained at a consistent rate of 17.4 m3/s across all scenarios, aligning with the mine’s standard air flow rate derived from the ventilation requirement for exhaust gases emitted by internal combustion engines of Load-Haul-Dump (LHD) machinery. With the duct’s terminal cross-sectional area at 0.8 m², this resulted in an inflow velocity averaging 21.75 m/s.Additionally, we included insights from three-dimensional numerical simulations performed in ANSYS Fluent, focusing on steady-state air movement and developed turbulence within the dead-end space. A comparative review of both empirical and modeled data shows that the ventilation jet, for all tested setback distances up to 21 m, successfully delivered air to the working face, where it then dispersed and initiated reverse flow patterns.These experiments led to the formulation of a linear relationship between the maximum relative velocity (compared to the initial jet velocity) at a distance of 1 m from the working face and a key geometric factor of the ventilation setup. This factor is the ratio of the duct’s setback distance to a characteristic dimension of the cross-sectional area, calculated as the square root of the cross-sectional area.
В статье рассмотрены проблемы проектирования систем обеспечения противопожарной защиты метрополитенов. Отмечено, что вопросам обеспечения пожарной безопасности на объектах метрополитенов уделяется особое внимание со стороны как контрольно-надзорных органов, так и специалистов, участвующих в разработке нормативных документов. При недостаточном уровне защиты от пожара нахождение в метрополитене чрезвычайно опасно, поскольку существует удаленность от поверхности и возможность быстрого задымления, что может привести к массовой гибели людей и значительным социально-экономическим последствиям. Предложены пути решения проблем, связанных с обеспечением пожарной безопасности метрополитенов. The article deals with the problematic issues of designing systems for ensuring fire protection of subways. To date, there is no precise definition of the functional fire hazard class for a metro station in regulatory documents. An object with a massive stay of people, primarily in terms of evacuation of people in case of fire, is considered one of the most difficult. Based on this fact alone, when designing a metro line and stations, special technical conditions are necessarily developed. The existing set of rules for subways is not included in the list of regulatory documents that ensure compliance with fire safety requirements. Many questions arise when designing smoke ventilation systems, since the provisions of the existing set of rules, as one of the main regulatory documents for the design of smoke protection systems, cannot be fully applied to underground metro structures. The parameters and modes of air exchange in an extensive metro network depend not only on the selected operating modes of ventilation equipment, but also on the piston effect from the movement of trains in tunnels, on the configuration of buildings and wind load in the area of ventilation shafts on the surface, season, etc. A separate important issue is ensuring the stability of the air flow in case of fire. In practice, the phenomenon of “overturning the jet” is known – a change in direction, a reversal of the movement of the air flow in the mine due to a change in pressure in the area with a fire. According to the set of rules, the stability of the air flow is ensured if the calculated speed of the air flow in the area exceeds the critical speed. The critical speed in this case depends only on the section of the tunnel and the slope. Neither the design power of the fire, nor other significant parameters are taken into account when determining it, which, of course, is not entirely correct from a physical point of view. The ways of solving problematic issues related to ensuring the fire safety of subways are proposed.
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