Study and application of a continuous inversion model of coal seam gas pressure in front area of heading face

Abstract

The gas pressure in front area of heading face is essential to dynamically evaluate coal and gas outburst during coal mining. In this work, a novel inversion model of gas pressure in front area of the heading face was established on premise of the hypothesis that a time-dependent zone of steady flow exists within newly exposed face. The key parameters in the inversion model were obtained based on the gas emission models and field data of gas emission rate in different times, which were used to calculate the volumes of gas emission from different sources. The results show that the percentage of gas emission from the heading face, coal wall and collapsed coal ranges from 7% to 47%, 47% to 82% and 2% to 11%, respectively. Based on the calculated volumes of gas emission and gas pressure inversion model, the gas pressure was obtained and transformed to the gas content. The absolute errors between the gas content tested and transformed in every hour is 0.4%–33%, which proved the rationality of gas pressure inversion model. Furthermore, the daily drifting footage, the radius of gas pressure boundary and the gas permeability coefficient of coal seam were confirmed to have a great effect on the result of gas pressure inversion. The inversion results verify that the speedy excavation can increase the risk of coal and gas outburst. This work produces a useful method for gas disaster prevention and control that converts the gas emission rate to an index of gas pressure within coal seam.