A new technology to enhance gas drainage in the composite coal seam with tectonic coal sublayer

Abstract

Composite coal seam is a kind of special coal seam that is formed after complex geological structure action, including a tectonic coal sublayer. Gas can't be drained easily from this coal seam, which cause coal and gas outburst accidents (CGOA) occur frequently. A new hydraulic flushing technology was proposed in this paper to improve gas drainage. Accordingly, a new set of mechanical equipment, technology process, roadway layout system and gas extraction monitoring system are provided by drawing lessons from the Guhanshan coal mine. The stress variation and damage failure were investigated by numerical simulation on the basis of flushed-out coal and borehole geometry. The gas drainage effect, coal seam permeability and outburst risk-sensitive indexes of the special coal seam were obtained by field measurements. According to the results, hydraulic flushing can enlarge the stress unloading and plastic damaged zone around boreholes dramatically, and the coal seam permeability can be increased largely.