Hydraulic Fracture Feature of Rock Under Unloading Based on Test and Numerical Simulation

• Published in: Geotechnical and geological engineering Vol. 42; no. 3; pp. 2221 - 2240
• Main Authors: Yang, Junyan, Wang, Meixia, Zhou, Zongqing, Yang, Weimin, Bai, Songsong, Zhang, Daosheng, Geng, Yang, Jiang, Pinglin, Ji, Xinwei, Lv, Pengfei
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.05.2024; Springer Nature B.V
• Subjects: Civil Engineering; Conduction; Crack propagation; Cracking (fracturing); Direction; Disasters; Dredging; Earth and Environmental Science; Earth Sciences; Energy release rate; Excavation; Failure modes; Geotechnical Engineering & Applied Earth Sciences; Horizontal orientation; Hydraulic fracturing; Hydraulics; Hydrogeology; Hydrostatic pressure; Mathematical models; Original Paper; Propagation; Rocks; Stress propagation; Terrestrial Pollution; Unloading; Waste Management/Waste Technology; Water; Water diversion; Water inrush; Water pressure; Laboratory Test; Fracture Propagation Model; Unloading Rate; Numerical Simulation; Hydraulic Fracturing
• ISSN: 0960-3182; 1573-1529
• DOI: 10.1007/s10706-023-02670-8

Water inrush results from excavation unloading and high water pressure coupling. To study the propagation mechanisms of hydraulic fracture and failure mode under unloading conditions, hydraulic fracturing tests and numerical simulations were carried out to study the effects of unloading rate, principal stress difference, and the angle of water-conducting cracks on crack propagation. The results showed that the failure mode is a splitting failure with a single crack under a low unloading rate, while the mode is a multi-crack failure under a high unloading rate. Rock fracture requires higher water pressure under slow unloading conditions, but the rupture time is shorter, and the energy release rate in the moment of failure is greater. During unloading with a low principal stress difference, when the angle between the prefabricated crack and the horizontal direction of the model θ  < 45°, the extension direction of hydraulic fracture is mainly controlled by the maximum principal stress direction. When θ  > 45°, the growth direction is controlled by the angle of the water diversion fissure. During unloading with a principal stress difference of 0, when θ  ≤ 30°, the propagation of hydraulic fracture is more easily controlled by the water conduction fracture. During unloading with a high principal stress difference, when θ  ≥ 30°, the maximum principal stress direction controls the propagation. The angle of the water-conducting fracture has little effect on the propagation direction of the main crack. The research in this paper is of great importance in studying the mechanism of water inrush disasters.