Ground stability of gob‐side entry by roof cutting in relation to mining stages: A case study

Abstract

In this study, we present a comprehensive investigation of the ground stability of a gob-side entry by roof cutting in relation to the mining stage, based on field measurements, theoretical analysis, numerical simulation, and in situ practice. Differing from the normal mode of gob-side entry, the mininginduced stress and strain evolution under gob-side entry by roof cutting (GSERC) is extremely complex, and unreasonable support can cause serious deformation and roof collapse of the GSERC. Taking Dadougou coal mine as the engineering background, a field investigation of the ground response, a rock mechanics experiment, and field measurement of the surrounding rock mass were first conducted. The roof-to-floor convergence presented an asymmetric deformation feature, based on the central axis. Numerical simulation is used to obtain results regarding the evolution of the second invariant of deviator stress and the third invariant of deviator stress (DSTI) in the primary use stage and the secondary reuse stage. It was found that the roof cutting action caused the peak value of the DSTI to transfer to the deep part of the roof. The DSTI value is greater than 0, indicating that tensile failure is dominant at 6-8 m of the roof above tailgate 5202, the upper part of the virgin coal rib, and 1.4 m away from the gangue rib. Finally, a support strategy for the following mining stages, including a support scheme for the primary use stage and the secondary reuse stage, is proposed based on the evolution law of the GSERC. The field-measured results demonstrate that this support strategy can effectively control the convergence of tailgate 5203, thus leading to a better environment for coal mining. Additionally, the proposed mining stage support strategy can provide a reference for other similar projects.