Solution of the Problem of Crack Opening by Methane in the Extremely Stressed Zone of the Formation


The conditions were studied concerning the cracks opening by in-situ methane in the formation marginal zone during its transition to the maximum stressed state. The calculations are based on the joint use of the fundamental methods of deformable solids mechanics, statics of the flowing medium, and the concept of academician S.A. Khristianovich on the distribution of pressure of intra-layer methane during the movement of the mine face at a constant speed.

The stress field of a coal-rock mass containing a seam with a weak interlayer and a working through it, was constructed within the framework of an elastic-plastic problem of the stressed state of a coal-rock mass. It is reduced to the integral equation of the second external boundary value problem of elasticity theory and solved by the boundary element method. The stress distribution in the extremely stressed zone of the formation is constructed by the method of characteristics known in the theory of differential equations.

In the model of the ultimate stress state of a structurally homogeneous formation, the limiting zones are formed from the edge itself. In the formation with an unstable interlayer, the interlayer passes to the limiting state first, and at some distance from the edge, the formation itself. After that, the formation and the intermediate layer are deformed as integral whole.

The cracks in the formation, which are its slip lines, open when the pressure of in-situ methane exceeds the stresses normal to the contour of the slip line. These stresses are related to the values of the principal stresses found from the solution of the boundary value problem. From this condition, the dimensions of the formation edge zone with free methane surfaces are determined.

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DOI: 10.24000/0409-2961-2022-2-13-19
Year: 2022
Issue num: February
Keywords : rock mass coal seam mine working extreme stressed zones resistance characteristics boundary problem of elasticity theory permeability coefficient porosity coefficient коэффициент фильтрации
  • Cherdantsev N.V.
    Dr. Sci. (Eng.), Chief Research Associate,, Federal Research Centre of Coal and Coal Chemistry of SO RAN, Kemerovo, Russian Federation