Gas-permeable zones in coal seams and the nature and mechanism by which they form

The mechanism by which gas-permeable zones around mine workings and borehol es form and develop is described, on the basis of in-situ observations of t he change of gas pressure in coal seams and the analysis of coal shrinkage and swelling during sorptional processes. It is shown that gas motion in th e coal seam may be regarded as a filtration wave with a jump in the sorbed gas at the front, coinciding with the moving boundary of the gas-permeable zone. Hooke's law relating the components of the stresses and elastic defor mations is presented, taking account of shrinkage and swelling of the coal during sorptional processes in the coal seams.