Abstract
A mechanical model of a hard roof was built to analyze the pressure relief roof cutting (RCPR) process for gob-side entry retaining (GER) and identify the critical stage of roadway stability control during RCPR. Based on the mechanical analysis of key parameters of automatic roadway with RCPR, the FLAC3D software was adopted to conduct a numerical simulation to investigate the influence law of height and angle of RCPR, to analyze the trend of variations in the vertical displacement of roadway surrounding rock stress and the roof under different conditions, and to verify that the optimal roof cutting height and seam cutting angle of the 12201 working face of Halagou Coal mine are 6 m and 20°, respectively. The effect of automatic roadway with RCPR has been well implemented through conducting the bidirectional cumulative blasting test on site. To impose effective roadway surrounding rock controlling measures on Halagou Coal mine in RCPR of hard, coal-bearing roof structures at a shallow mining depth, constant resistance large deformation anchor cables, in combination with a single hydraulic prop, joist steel 11#, and steel mesh reinforcement, could provide active surrounding rock support. In addition to the active support, surrounding rock control could be strengthened using grouting bolts. Based on the result, the stress in the roadway coal side and the vertical displacement of the roof can be reduced through increasing the roof cutting height, contributing to the stability of the roadway. Increasing of the roof cutting angle will lead to the increasing of stress in the coal side of the roadway and the increasing of roof displacement with a maximum angle of 20°. Meanwhile, the peak of stress concentrating on both sides of the extreme angle is decreased. Thus, increasing the cutting roof angle at random can be unfavorable to the management of roadway roof. To develop RCPR GER, roadway surrounding rock requires greater support when the mine face passes through a cutting slot. After industrial trials, these measures are proved to be effective in controlling surrounding rock movement and developing GER.
Highlights
Because of the recent breakthroughs in hydrogen, solar, wind, and other renewable energy technologies, coal energy production has steadily decreased over the years
No-pillar mining technology requires a roadway driving along the empty left lane of goafs to cut the top pressure relief [7]. is
In the RCPR gob-side entry retaining (GER) process, the structure of roadway surrounding rock is altered as the stress on the surrounding rock changes
Summary
Because of the recent breakthroughs in hydrogen, solar, wind, and other renewable energy technologies, coal energy production has steadily decreased over the years. In the Tangshan mine, a grass ditch mineral ore test revealed that [23, 24], because of its fully-mechanized coal face with a thin coal seam, the roadway falling height was relatively low, the strata deformation and stress change were relatively small, and low supporting strength was required for the lane This technique is rarely used in coal seams with medium thickness and above because, owing to the large roadway cutting height, large overburden movement deformation, and high stress variation of such coal seams, the technique has many adverse effects on the control of the roadway surrounding the cut rock and roof. Research was conducted regarding the hydraulic jacking cutting method of the mined-out area for upper strata migration. e corresponding supporting technology for the above operation in the thick coal seam is presented, focusing on the cuts that have not yet been performed for the unloading process of more than 7 m in coal seam mining
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