Abstract
In order to solve the problems of the high cost and time consumption of half coal rock entry driving, low coal recovery rate, and stress concentration on filling support body of retained entry along gob, the innovative 110 mining method based on pressure relief by roof cutting was adopted in 6302 thin coal seam working face of Baoshan Coal Mine. First the technical principle and key technology of this mining method was presented. Then, through theoretical analysis and calculation, engineering experience, and field test, the key parameters such as the length of constant resistance anchor cable, the cutting angle and height of presplitting blasting, the charge structure, and the blocking-gangue support structure were determined and conducted in the retained entry. The broken expanded coefficient varying law of caved gangue with time and space was obtained, which revealed roof movement characteristic. The displacement monitoring curve of the roof and floor indicated that the maximum subsidence of the roof was about 150 mm and the maximum amount of floor heaving was 100 mm, which were quite small. The field monitoring data indicated that the entry retaining effect is good, which indicated that the innovative 110 mining method can be an effective way for reducing the high cost and time consumption of half coal rock entry driving, enhancing the coal recovery rate and preventing the dynamic mine pressure disasters.
Highlights
Academician He et al put forward the theory of “short cantilever beam by cutting roof ”in 2008 [1], and based on this theory, He et al put forward the technology of pillarless mining with gob-side entry automatically retaining by roof cutting and pressure relief, that is, the 110 mining method
Gao et al [3] solved the problem that it was difficult to control the gangue rib caved along cutting structural plane in thick coal seam by establishing mechanical model, numerical simulation, and field test
Sun et al [4] analysed the stress state of roof in 1610 working face of Nantun Coal Mine and obtained the key parameters needed for gob-side entry retaining by roof cutting and pressure relief in thin coal seam
Summary
Academician He et al put forward the theory of “short cantilever beam by cutting roof ”in 2008 [1], and based on this theory, He et al put forward the technology of pillarless mining with gob-side entry automatically retaining by roof cutting and pressure relief, that is, the 110 mining method. Rough pressure relief by roof cutting, the roof structure and stress distribution of the surrounding rock of the entry were improved, and the entry side filling support body was replaced by the broken expanded caving gangue, which avoids the stress concentration on the filling body caused by dynamic roof pressure; the high cost and time consumption of half coal rock entry driving were reduced significantly, and the nonpillar mining was realized completely. 3. Key Techniques e technological process of 110 mining method is as follows: before the mining of the working face, the roof of the retaining entry was supported by constant resistance and large deformation anchor cable(CRLD anchor cable); along the entry strike, the directional presplitting cumulative blasting was carried out on the roof side of the working face; the roadside support was carried out after the working face was supported; after the working face was mined for a certain distance, the roof collapsed along the presplitting face and the caved gangue filled the gob due to the broken expanding effect, and the entry was retained. Thick layer, mainly composed of quartz and feldspar, semi-hard, hype-edge angle
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