Methane concentration in the worked-out space of the mining segment

Conclusions

In all the investigated ventilation layouts, large segments have been recorded in the worked-out space, where volume concentration of methane is consistent with Coward’s explosion triangle.

The volume of the explosion-prone zone is somewhat lower with a ventilation layout reverse with respect to the rock mass. This is determined by a greater reduction of the rate of outflow, beginning with distance from the cutting stretch, typical of the given section.

The comparatively short distance of the explosion-prone zones from the mined section with an outflow indicates feasibility of engineering installations securing mine safety through pumping in of neutral gases.

Maintaining a ventilating shaft behind the cutting stretch in a ventilation layout reverse with respect to the rock mass substantially removes the zone of higher methane concentration (at the established level of ventilation) from the working side.

Four characteristic variants of changes in methane concentration deeper into the worked-out space are theoretically possible depending on the character of inflow and filtration properties of rocks. In ventilation layouts considerably bending the outflow channels, and also in the presence of disturbing factors during unloading the coal measures, changes in methane concentration may be polyextreme.