Abstract
Gob-side entry retaining by roof cutting (GERRC) employed in a deep inclined thick coal seam (DITCS) can not only increase economic benefits and coal recovery, but also optimize surrounding rock structure. In accordance with the principles of GERRC, the technology of GERRC in DITCS is introduced and a roof-cutting mechanical model of GERRC is proposed to determine the key parameters of the depth and angle of RC. The results show that the greater the RC angle, the easier the caving of the goaf roof, but the length of cantilever beam increases. The depth of RC should account for the dip angle of the coal seam when the angle is above 20°. Increasing the coal seam dip angle could reduce the volume of rock falling of the goaf roof, but increase the filling height of the upper gangue to slide down. According to numerical model analysis of the stress and displacement of surrounding rock at different depths and angles of RC, when the depth of RC increased from 9 m to 13 m, the distance between the stress concentration zone and the coal side is increased. When the angle of RC increased from 0° to 20°, the value of roof separation is decreased. GERRC was applied in a DITCS with 11 m depth and 20° RC angle, and the field-measured data verified the conclusions of the numerical model.
Highlights
At present, most coal mines use retaining coal pillars to maintain the roadway
During mining of the working face, stress concentration is formed in the upper part of the coal pillar, causing large deformation and roof collapse of the entry, as well as geological disasters such as coal burst, and coal and gas outburst [2,3,4,5]
The rock of the goaf roof caved along the directional presplit face after mining and generated the gangue rib of entry (GERRC), with the gangue rib used for support to ensure that the gangue did not flow into the entry
Summary
Most coal mines use retaining coal pillars to maintain the roadway. The loss of coal pillars generally accounts for about 40% of the total coal loss of the whole mine [1]. Backward coal mining technology and methods reduce the rate of coal resource mining, with serious resource waste, and pose a huge threat to coal mine production. During mining of the working face, stress concentration is formed in the upper part of the coal pillar, causing large deformation and roof collapse of the entry, as well as geological disasters such as coal burst, and coal and gas outburst [2,3,4,5]. Gob-side entry retaining (GER) technology can improve the recovery rate of coal mining, and avoid major geological disasters. It is one of the sustainable development directions of coal mines
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