Estimation of stability of roadways surrounding rocks in a coal-rock stratum considering a deformation characteristics of secondary support structures

Abstract

Purpose. Evaluate the stability of the rocks surrounding the roadways in a coal-rock stratum, taking into account the deformation characteristics of supporting structures. Methodology. To achieve this goal laboratory study of the deformation characteristics of supporting structures located between the simulated roof and floor of the coal seam under uniaxial compression was performed. Results. This study demonstrates that the deformation characteristics of secondary support structures affect the stability of roadway surrounding rocks in a coal-rock stratum. The nature of the deformation of supporting structures under the action of external forces is specified by their stiffness. All other things being equal, when the roof and floor rocks have a constant flexural rigidity, their stability depends on the stiffness of the supporting structures and the direction of the load applied in the tangential (wooden crib supports: 4-point chock, sandwich chock) or radial (vertical timber sets) direction. For the simulated supporting structures with an increase in the compressive load was recorded a simultaneous linear increase in their stiffness and deformation modulus. Moreover, for wooden yielding crib supports, when the load is applying across the wood fibres, the compressed chocks of wooden cribs are compacted, because of which the roof-to-floor convergence is limited. There is no such pattern for rigid structures in the form of vertical timber sets. After the loss of stability of the supporting structure, the deformation modulus decreases, which is accompanied by an increase in the roof-to-floor convergence to the destruction of the construction. It is recommended to refuse to use rigid and fragile secondary support structures. Novelty. The roadways roof stability in the coal-rock stratum is estimated by the maximum relative deformation of the secondary support structures under uniaxial compression using a coefficient characterizing the ratio of the stiffness of the working supporting structure to flexural rigidity of the roof and floor strata. Practical significance. It is necessary to focus on the use of yielding supporting structures to ensure the stability of the immediate roof and floor of mine workings in the coal-rock stratum and the operational condition of the gateroads adjacent to the working face at the extraction site of the coal mine.