The problem of pore fracture growth in a marginal part of a gas-bearing coal seam

Abstract

The model of geomechanic state of the coal massif inclosing in-seam working driven along a gas-bearing seam is introduced in the paper. The model is built on the basis of the fundamental concepts of deformable body geomechanics and elastic fracture mechanics. It suggests that the massif is in the state of plane deformation loaded with a stress gravity field. It is assumed that strength characteristics of a coal seam are less than the strength characteristics of the inclosing seam rocks but higher than the strength characteristics along their contact. Coulomb-Mohr and Mohr-Kuznetsov strength criteria are taken as the condition for appearing of inelastic deformation. In this connection, the problem of stress-deformable state of a coal rock massif appears to be an elasticoplastic one. The pore gas pressure changes deep down the seam according to the hyperbolic tangent function. The model assumes that when setting the boundary condition on the seam contact with the side rocks the microfractures containing pore methane are oriented in the direction of a maximum principal stress.