Phase field model and numerical simulation study of hydraulic fractures for roadway roof pressure relief
LI Haolei
LIU Huaidong
LIU Changyou
YANG Jingxuan
CHEN Zhenhua
WU Fengfeng
Abstract：Hydraulic fracturing is one of the primary methods for stress relief in roadway sur-rounding rock(RSR).Great convergence difficulty,unclear interaction mechanism between fracture networks and stress evolution of RSR are encountered in the simulation of hydraulic fracturing in roadway roof.Based on phase field theory,the effective inversion of hydraulic fracturing crack propagation and surrounding rock stress relief in roadway roof was achieved by introducing initial energy terms into the potential energy equation and combining with initial stress balance technique.The fracturing range,fracturing degree and complexity of roadway roof crack networks were quantitatively characterized with damage area,damage density and fractal dimension as core indicators,and the mapping relationship between roof crack charac-teristics and surrounding rock stress relief effects was established.The results show that:The model exhibits high consistency with experimentalfracture propagation trajectories and demon-strates high accuracy for hydraulic fracturing calculations.The propagation behavior of subse-quent hydraulic fractures is controlled by pre-existing fractured cracks through regulating the roof stress field.Under the synergistic action of multiple fractures,high stress at crack tips is weakened and the transmission path to RSR is blocked,thus an effective stress relief zone is formed in RSR.The stress relief effect of RSR is negatively correlated with damage area,while positively correlated with damage density and fractal dimension.The stress relief effect of RSR follows a nonlinear evolution pattern of'first decreasing then increasing'as the lateral pressure coefficient increases from 0.8 to 1.6,with the optimal effect at a lateral pressure co-efficient of 0.8 and the worst effect at 1.2.To ensure better pressure relief effects in RSR,the fracturing spacing can be appropriately reduced and the inter-borehole angle increased to form high-density and high-complexity fracture networks.The research findings can provide certain engineering guidance for fracturing design.
Keywords：phase field theoryroof cutting for pressure reliefhydraulic fracturesnumerical simulationeffect evaluation
Publication Date：2025-09-30
Online Publishing Date：2025-10-31(First online date of this platform, not the publication date of the document)
Pages：13( 971-983 )