Sudden extrusion of an inhomogeneous coal seam: Basic relations

Abstract

Gas bursts are often confined to inhomogeneous boundaries in coal seams. Sudden extrusion of a worked coal seam is the initial stage of a gas burst. A mathematical model of the gas burst process was suggested by the present author and Kuznetsov using the approach suggested by Barenblatt and Khristianovich. A sudden extrusion of a worked seam, like a gas burst, is due to the formation of a zone of fractured coal. As a result, the rock pressure on the seam is redistributed and the process of sudden extrusion begins owing to convergence of the side rocks. From experience it is known that the zone of fractured coal is formed at the boundary between parts of the seam with different mechanical constants. The process of extrusion can be represented by a system of equations expressing the condition of conservation of mass for three sections of the plastic face zone. The results of computer calculations permitted conclusions to be drawn concerning constants and the depth of the seam below the surface on the possibility of a sudden extrusion.