Abstract
The application of gob-side entry retaining (GER) in steeply pitching seam longwall mining with a hard roof has always been a difficult problem. Based on the simplified roof beam mechanical model, the traditional gob-side entry retaining by packing (GERP) roof structure evolution process and its problems with use in steeply pitching seams are analyzed. Therefore, based on the unique characteristics of the gangue rolling and accumulating in the steeply pitching seam, this contribution proposes an innovative method of gob-side entry retaining by roof cutting (GERRC) in steeply pitching seam and details its technical process. The roof structures of the GERRC and the GERP are compared. Taking the Chang Gouyu Coal Mine as a case study, field experiments were carried out. This research finds that the GERRC can both overcome the impact of rolling gangue on roadside support and make the rolling and stacking gangue become a roadside support. The roof structure of the GERRC is in a one-time statically indeterminate state, which is conducive to the stability of the roadway. In the field test, the total displacement of the roadway roof and floor is 97 mm, the supporting pressure of the serried single props is less than 28 MPa, and the props have no obvious bending phenomenon.
Highlights
Gob-side entry retaining (GER) refers to maintaining either headentry or tailentry behind the working face by constructing a fill-in sidewall on the gob side with special support to be reused for the panel [1, 2]
Based on the unique characteristics of gangue rolling and accumulating in the gob of steeply pitching seams, this paper proposes an innovative method, the gob-side entry retaining by roof cutting (GERRC) in steeply pitching seams
According to the different roof structures of the gob-side entry retaining by packing (GERP), the roadway can be divided into three areas: advance area of the working face, arc triangle block unbroken area in the gob, and arc triangle block broken area in the gob
Summary
Gob-side entry retaining (GER) refers to maintaining either headentry or tailentry behind the working face by constructing a fill-in sidewall on the gob side with special support to be reused for the panel [1, 2]. This technology has obvious advantages in improving coal recovery, and reducing roadway development, while solving the problem of gas accumulation. For a steeply pitching seam (35°~55°), the natural stop angle of gangue in the gob is less than the coal seam dip angle, and the gangue will naturally roll and accumulate in the lower end of the working face.
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