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Coal Engineering ›› 2026, Vol. 58 ›› Issue (7): 167-175.doi: 10.11799/ce202607021

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Construction and application of a quantitative fracability evaluation model for thick and hard coal seam roofs#br#

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  • Received:2025-07-18 Revised:2025-09-01 Online:2026-07-15 Published:2026-08-03
  • Contact: peng wang E-mail:wpeng1205@sina.com

Abstract:

Fracturing hard, thick roof strata is a critical step in coal mining. Currently in China, the control of hard, difficult-to-cave roofs primarily relies on blasting, supplemented by water injection softening. In recent years, advancements in hydraulic fracturing technology have provided robust technical support for fracturing coal seam roofs. The targeted selection of fracturing zones and intervals is key to improving fracturing efficiency. Therefore, this study, taking sandstone samples from the roof of the Caojiatan Coal Mine in Shaanxi as an example, established a quantitative fracability evaluation model for coal seam roofs through integrated methods including XRD, triaxial stress tests, and fracture toughness experiments. A standardized fracability evaluation index was constructed. The results indicate that the Fracability Index (FI) is most significantly influenced by rock brittleness, with lesser impacts from fracture toughness and natural fractures. When the Fracability Index FI > 0.53, the rock is most amenable to fracturing. This evaluation index enables the quantitative assessment of the fracability of target roof strata in coal seams, providing direct methodological support for selecting fracturing zones and intervals. The research findings can directly guide fracability evaluation of the roof and provide a basis for subsequent fracturing design.

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