Abstract
A case study based on the 401103 fully mechanized caving face in the Hujiahe Coal Mine was carried out in this research to analyze the rock burst risks in a 54 m-wide coal pillar for roadway protection. Influencing factors of rock burst risks on the working face were analyzed. Stress distribution characteristics on the working face of the wide coal pillar for roadway protection were discussed using FLAC3D numerical simulation software. Spatial distribution characteristics of historical impact events on the working face were also investigated using the microseismic monitoring method. Results show that mining depth, geological structure, outburst proneness of coal strata, roof strata structure, adjacent mining area, and mining influence of the current working face are the main influencing factors of rock burst on the working face. Owing to the collaborative effects of front abutment pressure of the working face and lateral abutment pressure in the goaf, the coal pillar is in the ultimate equilibrium state and microseismic events mainly concentrate in places surrounding the coal pillars. Hence, wide coal pillars become the regions with rock burst risks on the working face. The working face adopts some local prevention technologies, such as pressure relief through presplitting blasting in roof, pressure relief through large-diameter pores in coal seam, coal seam water injection, pressure relief through large-diameter pores at bottom corners, and pressure relief through blasting at bottom corners. Moreover, some regional prevention technologies were proposed for narrow coal pillar for roadway protection, including gob-side entry, layer mining, and fully mechanized top-coal caving face with premining top layer.
Highlights
Rock burst is a dynamic phenomenon that is produced by releasing deformation energies from the roadway or surrounding coal rocks, with characteristics of sudden, sharp, and great damages
Accumulative elastic energy in coal rocks increases with the increase of mining depth, which increases the possibility of rock burst event [16, 17]. e buried depth of coal seams on the 401103 working face is 730 m, which can significantly influence rock burst
According to the statistical analysis on historical rock burst events during mining of the 401103 working face, seismic sources of rock burst are concentrated in areas close to the section coal pillars, while rock burst events occur in the intake airway. is is mainly because high static loads are formed in wide coal pillars owing to the influences of the lateral abutment pressure in the gob
Summary
Rock burst is a dynamic phenomenon that is produced by releasing deformation energies from the roadway or surrounding coal rocks, with characteristics of sudden, sharp, and great damages. Many studies on rock burst risks and determination of reasonable width of coal pillars in coal seams with strong burst proneness have been reported in China. Wang et al [11] used burst initiation theory combined with the space structure of overlying strata to investigate the space structural characteristics of overlying strata on the island working face as well as the distribution and variation laws of stress fields in mining surrounding rocks through a similarity simulation test. Ere are the 401 mining area and boundary coal pillars of Xiaozhuang well field in the south, 401102 fully mechanized caving face in the west, and coal pillars for roadway protection in the 401 panel in the east. On the 401103 working face, the gob-side advancing roadway is the intake airway, where coal pillars have a width of 54 m. e ground elevation of the working face ranges from +920.6 m to +1070.7 m, while the elevation of the coal seam floor ranges from +340 m to +350 m. e strike length and proneness length are 1643 and 190 m, respectively. e 4 fourth coal bed pitch, thickness, and hardness are 0°–3°, 25.0–28.0 m, and 1.8–2.4, respectively. e 401103 working face adopts the long wall layered fully mechanized top-coal mining. e heights of the cutting coals and coal caving are 3.5 and 10.0 m, respectively
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