Failure evolution mechanism of the end-area hanging roof of a coal mining face under static fracturing effects

Yuan Ruifu; Li Hui; Dong Zhuo; Zhang Qunlei

doi:10.16186/j.cnki.1673-9787.2024120020

Abstract：Objectives To reveal the failure evolution mechanism of the end-area hanging roof of a coal min-ing face and to achieve rational mine pressure control,this study investigates the static fracturing failure characteristics of the hanging roof and determines the optimal drilling spacing.Methods A numerical model of end-area hanging roof failure was established using the Continuous-Discontinuous Element Method(CDEM)to analyze the static fracturing failure characteristics.Based on the geological conditions of the 5-2 coal seam in a representative mine,a numerical model of the strata in the end area of the working face was constructed to investigate the deformation and fracture processes of the hanging roof before and after static fracturing during excavation,thereby revealing the failure evolution mechanism under the action of static cracking agents.Results The results indicate that the expansion pressure of the static cracking agent is positively correlated with the tensile strength of the hanging roof.When the tensile strength is lower than 8 MPa and the expansion pressure is≥30 MPa,optimal fracturing performance is achieved.The optimal drilling spacing for hanging roof fracturing is 1.25 m.Before static fracturing,the periodic caving interval of the end-area hanging roof ranges from 37.5 m to 22.5 m,with an average interval of 27.5 m.After static fracturing,the periodic caving interval is reduced to 17 m to 12 m.Field measurements of support resis-tance and roof displacement further verify the feasibility of the static fracturing technique.Conclusions By regulating the caving interval and fracture sequence of the hanging roof,static fracturing technology can ef-fectively mitigate safety hazards induced by sudden mine pressure variations.The findings provide theoreti-cal guidance for the engineering application of static fracturing technology in hard roof control.