Investigation on breakage and collapse characteristics of hard and thick roof during coal excavation subject to hydraulic fracturing

• Published in: Engineering failure analysis Vol. 181; p. 109935
• Main Authors: Wang, Xiaohua, Feng, Yanjun, Zhang, Fengshou, Zhao, Kaikai, Yin, Zirui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2025
• Subjects: Engineering disaster; Geological engineering; Ground fracturing; Numerical simulation; Rock mechanics; Ground fracturing; Numerical simulation; Engineering disaster; Geological engineering; Rock mechanics
• ISSN: 1350-6307
• DOI: 10.1016/j.engfailanal.2025.109935

•A numerical model of HTR instability during coal mining is developed.•A study on the response characteristics of HTR before and after hydraulic fracturing is conducted.•Impact of fracture spacing, fracture height, and fracturing horizon on roof collapse is revealed. During the excavation of thick to extremely thick coal seams, the large-span suspension of the overlying hard and thick roof (HTR), which is resistant to natural collapse, can readily induce dynamic disasters in mines. Ground hydraulic fracturing, an essential stratum preconditioning technique, utilizes high-pressure fluid injection to create multiple fractures in HTR, which facilitates roof collapse through pre-engineered structural weakening during longwall mining operations. However, the breakage and collapse characteristics of HTR under the influence of critical engineering factors related to hydraulic fracturing remain unclear. Therefore, this paper takes the X Coal Mine in China as the background, and develops a numerical model for simulating roof collapse during coal mining incorporating hydraulic fracturing of HTR based on the distinct element code. A comparative study on the dynamic response characteristics of HTR before and after hydraulic fracturing is conducted, with a focus on elucidating the influence of key engineering parameters such as fracture spacing, fracture height, and fracturing horizon. The study reveals that low fracture spacing, large fracture height, and optimal fracturing horizon promote the sustained collapse of HTR, thereby effectively reducing the likelihood of long-span instability. Therefore, employing closely-spaced and high-intensity hydraulic fracturing of HTR emerges as a crucial measure to ensure controlled caving. This research offers valuable theoretical support and technical insights into the weakening of HTR through hydraulic fracturing, ultimately contributing to the enhancement of safe and efficient coal production practices.