Strain field response to cross-interface propagation in DIC-based roof-guiding hydraulic fracture networks
MA Yankun1, 2, 3, LIU Hongjie1, 2, 3, ZHAO Aohan1, 2, 3, MA Dengyun1, 2, 3, WANG Guyu1, 2, 3, ZHANG Xi1, 2, 3
(1. Key Laboratory of Coal Mine Safety and Efficiency Co-constructed by the Ministry of Education, Anhui University of Science and Technology, Huainan, Anhui 232001, China; 2. Safe and Efficient Mining Anhui University Engineering Technology Research
Center, Anhui University of Science and Technology, Huainan, Anhui 232001, China; 3. Coal Mine Deep Mining Disaster
Prevention Technology Research and Development Platform, Anhui University of Science and Technology,
Huainan, Anhui 232001, China)
Abstract：Roof-guided hydraulic fracturing technology presents significant potential for regional gas drainage in outburst-prone coal seams. To investigate the dynamic cross-interface propagation behavior of fractures, we conducted hydraulic fracturing experiments on “roof rock-coal” composite specimens using a self-developed true triaxial fracturing system equipped with visual observation capabilities. Real-time fracture propagation was monitored through an observation window, while digital image correlation (DIC) was employed to analyze the evolution of the strain field during cross-interface fracture extension. Key findings include: (1) Significant heterogeneous deformation was observed during fracture propagation, with distinct zones of tensile and compressive strain localization flanking the fracture. Fractures predominantly developed within the tensile strain localization zones, with propagation paths closely aligned with the morphology of these zones. (2) The influence ranges of the tensile and compressive strain localization zones measured 532–706 times and 459–481 times the fracture width, respectively. During cross-interface propagation, strain fields exhibited marked disparities across the rock-coal interface, with strain localization zones extending into the adjacent medium as fractures advanced. (3) Propagation rates were notably lower in the roof strata, where fracture-tip tensile strain localization zones were short and wide. Conversely, higher propagation rates were observed in lower-strength coal seams, characterized by long and narrow tensile strain localization zones at fracture tips. (4) Fracture path deviation occurred due to shear strain generation at fracture tips induced by coal-rock heterogeneity. Propagation paths consistently followed the direction of maximum shear strain intensity, resulting in a tensile-shear (Mode I-II) hybrid fracture morphology.
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2025, Vol. 44 
