Early reduction of the burst hazard of a coal seam by hydroseparation

Abstract

1. In the influence zone of hydroseparation holes, where aquatic solutions of hydrochloric acid and surfactants were used as the working fluid, no gas-dynamic phenomena occurred during the course of drifting. Hazard indicators R1 and K1 had values below the critical. 2. The use of aqueous solutions of hydrochloric acid and surfactants provided uniform wetting of the coal seam. Because the holes were not developed, there was an increase of excessive moisture content in the seam by 1.1–1.9%, and reduced gas permeability. 3. The coal hardness decreased insignificantly as the working advanced into the hydroseparation zone. The drainage of the seam restored it to the level of untreated mass. 4. The yield of drilling fines from the holes showed that the hydroseparation of burst-hazardous coal seams by water solutions of hydrochloric acid and surfactants loosens the coal seam and slackens the stresses in the face area. 5. The gas permeability of the coal seam after hydraulic separation without hole development was slightly increased. In order to enhance the seam permeability, hydroseparation should be followed by drainage and degassing, and, before the excavation work, additional water should be added to lower the sorption potential of the “coal-working liquid-gas” system. 6. The use of aqueous solutions of 4–6% hydrochloric acid with the addition of 0.1–0.5% noniogenic surfactant ensured a faster antiburst treatment of the coal seam compared to treatment with water alone. 7. The tests have determined that the burst hazard of a thick, gentle sloping coal seam in the hydroseparation zones is reduced, demonstrating that the use of aqueous solutions of hydrochloric acid and surfactants in the Karaganda Basin could allow abandoning local antiburst measures and thus enhance the technicoeconomic efficiency of the operation on development and breakage segments in burst-hazardous seams.