Characteristics of stress sources and comprehensive control strategies for surrounding rocks of gob-side driving entry in extra thick coal seam
The control technology for surrounding rocks of gob-side driving entry in 14-20 m coal seams is one of the challenges in the field of roadway support.A gob-side entry driving with small pillar in fully mechanized caving face around goaf of 19 m coal seam in Shanxi Coal International Energy Group Co.,Ltd.,was selected as the research object.The structural char-acteristics of stress arch and fracture arch of the overlying rocks,as well as the lateral fracture movement characteristics of the main roof were analyzed.A dual-stress-source model for the gob-side entry driving of the thick coal seam was proposed to reveal the transmission mecha-nism of the stress sources and its impact on the stability of the surrounding rocks.Moreover,a comprehensive control strategy of far-field-weakening and near-field-strengthening was pro-posed.An industrial test of the surrounding rock control for the gob-side entry driving with 8 m coal pillar in 19 m extra thick coal seam was conducted on site.The results show that the strong stress of the gob-side entry driving is caused by the superposition of mode Ⅰ stress source from the small coal pillar side and mode Ⅱ stress source from the entity coal side.The pressure step distance of the main roof is reduced by about 69.6％after implementing the weakening technology of hydraulic fracturing and deep blasting at the small coal pillar side(mode Ⅰ)and entity coal side(mode Ⅱ),effectively blocking the transmission of mining stress to the surrounding rock.Meanwhile,combined with the strengthening support technolo-gy,the stability of the gob-side entry driving is effectively controlled.The research results have theoretical and engineering guidance significance for safe,efficient,and high recovery mining of 14-20 m thick coal seams.
extra thick coal seamgob-side entry drivingdual-stress-source modelfar-field-weakeningnear-field-strengthening
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