Abstract
A small-pillar gob-side roadway showed rockburst appearance during the mining of a gob-side working face located in the Shaanxi-Inner Mongolia mining area. This study examines the 2202 gob-side working face of a coal mine in Inner Mongolia as a case study. A stress evolution model was built for the static-stress spatial islands formed by drainage regions and goafs based on the spatial relationships between drainage regions and goafs. The average microseismic frequency and energy of the high-stress zone of spatial islands were at least 1.37 times of those of other zones, validating the presence of spatial islands. The dynamic and static load effects of working face squaring were obtained based on the evolution of the stope roof as well as changes in microseismic data. Microseismically active zones were advanced to 200 m–300 m on working faces. The rockbursts induced by high static loads and dynamic and static loads formed by spatial islands and squaring were calculated. According to calculation results, the critical stress concentration value under high static loads was 3.27; the critical static stress concentration value under dynamic and static loads was 1.81. The superposition of drainage boundary stress, goaf lateral stress, and lead stress might reach the critical stress concentration under dynamic load disturbances, causing rockbursts. A stress adjustment scheme was established, including overall hydraulic fracturing of the external roof of the drainage region, reduction of stoping speed, and pressure relief of large-diameter boreholes. The stress adjustment scheme was implemented on-site and supplemented by monitoring and early warning methods to safely advance by the first squaring region.
Highlights
Rockburst manifestations were primarily related to working face squaring and spatial island working faces, so we primarily collected and sorted through existing data related to both spatial island working faces and squaring
Yang et al [17] proposed putting the rockbursts of island working faces under “classified control” and classified island working faces into six types, that is, island working faces with critical extraction on both sides, island working faces with subcritical extraction on both sides, island working faces with critical extraction on one side, and subcritical extraction on the other side, stereoscopic island working faces formed by goafs of different coal seams, hidden island working faces formed by geological structures, and composite island working faces formed by a geological structure-goaf
With regard to the obvious dynamic phenomena occurring on the gob side of a spatial island working face, the formation and stress evolution process of the spatial island working face were explored using theoretical analysis as well as on-site monitoring. e force sources behind its rockburst appearance were analyzed. e mechanism of rockburst induced by high static loads and by dynamic and static loads under the combined action of spatial islands and working face squaring was clarified, and control measures were prepared
Summary
Rockbursts are one of the most serious dynamic disasters threatening coal mine safety. Cao et al [15] theoretically examined how the spatial structure and rupture movement of thick and hard overburden of island working faces would affect mine earthquake activities. Island working faces are generally classified as either plane island working faces (formed by goafs on the two sides of the same coal seam) or spatial island working faces (formed by goafs on the two sides of different coal seams, formed by faults and goafs, or formed by drainage regions and goafs (under investigation in this study)). Many experts and scholars have extensively studied spatial island working faces (formed by two goafs of different coal seams or formed by faults and goafs). Is study primarily investigated a type of novel static-stress spatial islands formed by roof drainage regions and goafs. With regard to the obvious dynamic phenomena occurring on the gob side of a spatial island working face, the formation and stress evolution process of the spatial island working face were explored using theoretical analysis as well as on-site monitoring. e force sources behind its rockburst appearance were analyzed. e mechanism of rockburst induced by high static loads and by dynamic and static loads under the combined action of spatial islands and working face squaring was clarified, and control measures were prepared
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