Experimental study on fractures propagation law and fractures mechanism of gel fracturing

LIN Yukun; LIU Jiangwei; CHEN Shaojie; LI Nan; WANG Xiaofei; LIU Yaoyou; LU Zhiyuan

doi:10.12438/cst.2024-1745

Abstract：Hydraulic fracturing is a widely used physical rock-breaking method to address the challenges in cutting hard rocks.However,conventional water-based fracturing typically generates fractures propagating perpendicular to the minimum principal stress direction,res-ulting in limited fractures quantity and simplistic morphology,which restricts rock-breaking efficiency and productivity in mining opera-tions.To enhance rock fragmentation effectiveness,this study proposes a novel gel fracturing technique.Based on the self-developed true triaxial hydraulic fracturing simulation experiment system of coal and rock mass,pure water fracturing,gel fracturing after pure water frac-turing and gel fracturing experiments with different mass fractions were carried out.An electronic pressure recorder was employed for real-time monitoring of specimen rupture pressures,enabling comparative analysis of pressure evolution patterns and corresponding fracturing behaviors.By comparing and analyzing the macroscopic fractures characteristics of the test block,the fractures propagation law of gel fracturing was explored,and the rock breaking mechanism of gel fracturing was revealed.The key findings demonstrate that:①Gel frac-turing significantly increases fractures density,enhancing total fractures length per unit area by 92.71%-216.67%and fractures density by 92.7%-216.97%,while creating more complex fractures networks;②Prolonged and substantial pressure fluctuations during gel fractur-ing represent mechanical responses to complex fractures formation;③Gel fracturing reduces rock fragment size while enlarging fractures apertures,generating significantly more branch fractures than water fracturing,with markedly superior rock-breaking performance;④Higher gel concentration correlates with increased branch fractures and more pronounced fracturing dynamics.These results confirm that gel fracturing fundamentally alters conventional fractures propagation patterns through temporary sealing of initial fractures by block-ing agents during fractures initiation and extension phases.This mechanism modifies stress distribution in weak zones to initiate new frac-tures,achieving substantially better rock fragmentation than water fracturing.The findings provide theoretical support for optimizing hy-draulic fracturing techniques in hard rock excavation.