An experimental study on the compressive shear failure characteristics of mining-induced fractured rock blocks in the absence of lateral confinement and under unilateral confinement

Authors

• WANG Wenxue, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, ChinaFollow
• ZHANG Shicheng, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China
• LI Linyang, College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
• ZHANG Ruochen, School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
• LIANG Yankun, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China
• CHANG Jian, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China
• PAN Xuwei, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China
• ZHAO Guizhang, Henan Province Key Laboratory of Rock and Soil Mechanics and Structural Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, China

Abstract

Objective Rock bridges exert a controlling influence on the deformation, fracture field evolution, and structural stability of mining-induced fractured rock masses. Therefore, it is necessary to investigate their deformation and failure characteristics, as well as the underlying controlling mechanisms, under different confinement conditions. Such investigations will provide theoretical support for the safe mining of underground coal seams and the prevention and control of mining-induced disasters. Methods Mechanical models of fractured rock blocks containing rock bridges were established. Specimens with different fracture dip angles, rock bridge widths, and material strengths were prepared using rock-like materials. Furthermore, an independently developed compressive shear testing system capable of applying lateral confinement was employed to conduct compressive shear failure tests on the specimens under two conditions: in the absence of lateral confinement and under unilateral confinement. Results and Conclusions The load-displacement curves reveal that in the absence of lateral confinement, the specimens underwent three evolutionary stages: compaction accompanied by fracture initiation and propagation, post-peak failure induced by fracture penetration, and residual frictional equilibrium. Without lateral confinement, the rock bridge failure load increased linearly with material strength and rock bridge width, while showing a negative linear correlation with the sine of the fracture dip angle. Furthermore, the cohesion and internal friction angles obtained by analyzing the stresses acting on the rock bridge interfaces in the mechanical models exhibited relative errors of consistently less than 5.8% compared to the results of double-sided shear tests. Under unilateral confinement, the rock bridge failure load increased by an average of 41.64%, with the failure mechanisms governed by the fracture dip angle. Specifically, specimens with fracture dip angles of 57° or 75° primarily exhibited lateral contraction prior to rock bridge failure, while the normal load remained relatively low. Following rock bridge failure, the specimens experienced outward expansion, resulting in a sharp increase in normal load. In contrast, specimens with a fracture dip angle of 90° underwent lateral expansion during the initial loading stage due to the tension-shear effect. Concurrently, the normal load applied to the specimens increased with continued loading and gradually stabilized after the penetration failure of rock bridges. The vertical load transfer coefficient increased as the fracture dip angle decreased and increased slightly with specimen strength due to the limited influence of the latter. These findings indicate that rock blocks with high strength and low fracture dip angles exhibit greater load transfer efficiency. The results of this study provide a theoretical basis and novel experimental approaches for evaluating the stability and determining the strength parameters of mining-induced fractured rock masses.

Keywords

fractured rock block, rock bridge, compressive shear test, shear strength parameter, unilateral confinement, failure characteristic

DOI

10.12363/issn.1001-1986.26.04.0206

Recommended Citation

WANG Wenxue, ZHANG Shicheng, LI Linyang, et al. (2026) "An experimental study on the compressive shear failure characteristics of mining-induced fractured rock blocks in the absence of lateral confinement and under unilateral confinement," Coal Geology & Exploration: Vol. 54: Iss. 8, Article 17.
DOI: 10.12363/issn.1001-1986.26.04.0206
Available at: https://cge.researchcommons.org/journal/vol54/iss8/17

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