Duan Guoyong, Zhou Yuchen, Li Fei, Wang Yanhai
Hubei Key Laboratory of Disaster Prevention Mitigation (China Three Gorges University), Yichang, China.
Key Laboratory of Geological Hazards on Three Gorges Reservoir Area (China Three Gorges University), Ministry of Education, Yichang, China.
Sci Rep. 2025 Apr 24;15(1):14290. doi: 10.1038/s41598-025-98600-0.
Variable angle structural surfaces are more common in slopes. However, variable-angle joints have still been approximated as single-angle straight joint planes for analysis in previous studies, which failed to comprehensively capture the mechanical properties of such surfaces. In this paper, joint specimens with variable angles were fabricated using concrete. Direct shear tests were carried out under different normal stress conditions, and the strength, deformation, and failure characteristics of the specimens were analyzed. The results revealed a significant positive correlation between the peak shear strength and shear stiffness of the variable angle specimens with the normal stress, while the correlation between the residual shear strength and the normal stress was relatively insignificant. The normal displacement and tangential displacement of the specimen exhibited a significant negative correlation. When shear failure occurred, the main cracks propagated along the shear direction, accompanied by localized secondary cracks and surface spalling. Unlike the straight joints commonly studied in previous research, variable-angle joint specimens exhibit distinct failure modes in the high-angle zone and the low-angle zone. In the high-angle zone, vertical cracks perpendicular to the joint surface and shear cracks along the shear direction predominantly occurred. The low-angle zone was dominated by shear damage along the shear direction. By comparing the results of experimental tests and theoretical analysis, the zonal pattern of shear failure characteristics on variable angle surfaces was revealed. The research findings provide a theoretical basis for the safety and stability analysis of variable angle structural surfaces.
变角度结构面在边坡中更为常见。然而，在以往的研究中，变角度节理仍被近似为单角度直节理面进行分析，未能全面捕捉此类结构面的力学特性。本文采用混凝土制作了变角度节理试件。在不同法向应力条件下进行了直剪试验，并对试件的强度、变形和破坏特性进行了分析。结果表明，变角度试件的峰值抗剪强度和抗剪刚度与法向应力呈显著正相关，而残余抗剪强度与法向应力的相关性相对较小。试件的法向位移和切向位移呈显著负相关。当发生剪切破坏时，主裂缝沿剪切方向扩展，伴有局部次生裂缝和表面剥落。与以往研究中常见的直节理不同，变角度节理试件在高角度区和低角度区呈现出不同的破坏模式。在高角度区，主要出现垂直于节理面的竖向裂缝和沿剪切方向的剪切裂缝。低角度区以沿剪切方向的剪切破坏为主。通过对比试验测试结果和理论分析，揭示了变角度结构面剪切破坏特征的分区模式。研究结果为变角度结构面的安全稳定性分析提供了理论依据。
