Spatiotemporal evolution of fractures in hydraulic fracturing for roof cutting and pressure relief in Menkeqing Coal Mine

WU Shaoguo; WANG Yuanjie; SU Shijie; ZHAO Qian; LIU Ning; LI Yan

doi:10.11799/ce202510009

Abstract：To clarify the spatiotemporal evolution patterns of rock fissures during hydraulic fracturing for roof cutting and pressure relief in coal mines,a coupled model of hydraulic fissures propagation and particles migration was developed using discrete element method.We systematically analyzed the response patterns of fissures number and morphology,particles migration characteristics,and damage zone area to water pressure,cohesion,porosity,and Young modulus.The results show that:Firstly,increased water pressure promotes the transition of fissures from linear propagation to complex network or branching morphologies,providing more channels for particles migration and thereby expanding the damage zone area.However,excessively high water pressure induces a compaction effect,reducing the effectiveness of fracture channels and inhibiting damage zone expansion.Secondly,increased cohesion leads to more regular fissures propagation,shifting particles displacement patterns from disordered to ordered.Porosity affects the complexity of fissures propagation and the magnitude of particle displacement,with optimal particles displacement range and magnitude observed under medium porosity conditions.Increased Young modulus results in more concentrated fissures propagation paths and significantly enhanced directionality of particles displacement.Thirdly,the temporal evolution of fissures can be divided into an initiation stage(no fissure growth),a micro-crack propagation stage(slow fissures growth),and a rapid crack propagation stage(stable and rapid fissures growth).The temporal evolution curves of hydraulic fissures under different variable conditions all follow an exponential function distribution.The research findings provide theoretical support for optimizing process parameters and improving the effectiveness of hydraulic fracturing for roof cutting and pressure relief in coal mine roofs.