Effect of Nitrogen Injection on Distribution of Oxidation Zone in Goafs Under the Roof Cutting and Pressure Relief Mining Mode with Z-Type Ventilation

The mining mode of retained roadway by roof cutting and pressure relief (RCPR mining mode) is being popularized for no coal pillar and decrease in roadway excavation. However, this mining mode changes the ventilation form of the mining face, influencing spontaneous coal combustion in a goaf. To reveal the distribution of spontaneous coal combustion and the disaster prevention effect of nitrogen injection in a goaf under this mining mode, the distribution of oxidation zone is compared under the traditional mining mode and RCPR mining mode, followed by the nitrogen injection simulation. The results show that (1) The return-airway-side oxidation zone is 52% wider under RCPR mining than under traditional mining; (2) Nitrogen injection narrows the intake-airway-side oxidation zone, with an optimal location 115 m behind the mining face; (3) Nitrogen injection reduces the maximum oxidation zone temperature, with an optimal flow rate of 1400 m3/h.