Key Takeaways & Executive Findings
- •• Increasing initial normal load (Fsd) from 7.5 to 120 kN enhances peak and residual shear loads by up to 35.25% and 86.74%, respectively, indicating a strong positive effect on load-bearing capacity. • Shear wear predominantly occurs during the initial cyclic shear stage, as the maximum shear load per cycle declines and stabilizes over subsequent cycles. • Cyclic shearing induces continuous shear contraction, with normal displacement decreasing spirally; later cycles are dominated by dynamic sliding along pre-existing shear rupture surfaces, especially in coal. • The bearing capacity and failure mode of the anchoring system are rock-type dependent, with debonding predominantly occurring at the resin–rock interface, and damage severity modulated by rock type.
Abstract
This study investigated the mechanical responses and debonding mechanisms of a bolt–resin–rock composite anchoring system subjected to cyclic shear loading. A systematic analysis was conducted on the effects of the initial normal load (Fsd), cyclic shear displacement amplitude (ud), frequency (f), and rock type on the shear load, normal displacement, shear wear characteristics, and strain field evolution. The experimental results showed that as Fsd increased from 7.5 to 120 kN, both the peak and residual shear loads exhibited increasing trends, with increments ranging from 1.98% to 35.25% and from 32.09% to 86.74%, respectively. The maximum shear load of each cycle declined over the cyclic shear cycles, with the rate of decrease slowing and stabilizing, indicating that shear wear primarily occurred at the initial cyclic shear stage. During cyclic shearing, the normal displacement decreased spirally with the shear displacement, implying continuous shear contraction. The spiral curves display sparse upwards and dense downward trends, with later cycles dominated by dynamic sliding along the pre-existing shear rupture surface, which is particularly evident in coal. The bearing capacity of the anchoring system varies with the rock type and is governed by the coal strength in coal, resin–rock bonding in sandstone#1 and sandstone#2, combined resin strength and resin–rock bonding in sandstone#3 (sandstone#1, sandstone#2 and sandstone#3, increasing strength order), and resin strength and bolt–resin bonding in limestone. Cyclic shear loading induces anisotropic interfacial degradation, characterized by escalating strain concentrations and predominant resin–rock interface debonding, with the damage severity modulated by the rock type.
1. Introduction
Anchoring support is recognized as an effective technique for underground engineering stabilization and is renowned for its capacity to swiftly establish an integrated load-bearing structure between the surrounding rock and support system, thereby effectively harnessing the inherent stability of the rock mass and maximizing its load-bearing potential [1–5]. This proactive support method has not only significantly enhanced the long-term stability of roadways but has also gained widespread application in engineering construction because of its low labor intensity, high efficiency, and pronounced economic benefits [6–9]. However, underground anchoring systems are inevitably subjected to dynamic loads, such as mining activities, roof collapses, and mechanical disturbances, which can significantly affect their mechanical properties and load-bearing capabilities, as depicted in Fig. 1. The potential for system failure, primarily characterized by debonding at the interfaces between the bolt and anchoring agent and between the anchoring agent and the surrounding rock, poses a significant threat to the stability of the anchoring system [10–12]. Consequently, an in-depth investigation into the mechanical characteristics and failure mechanisms of anchoring systems under dynamic disturbances is critical for ensuring the safety of underground engineering operations.
Traditional pullout tests, which provide a macroscopic assessment of the overall bearing capacity of anchoring systems, have a limited ability to elucidate interactions at anisotropic interfaces between dissimilar materials because of the inherently concealed nature of interfacial mechanics. Shi et al. [13] studied the prestress loss in bolts based on laboratory pullout tests, and the results indicated that the shear-dilatancy effect between the bolt and rock is a key factor in inducing debonding failure. Fu et al. [14] investigated the relationship between the maximum anchorage force and the anchorage length in a hard rock context, providing insights into the load transfer mechanisms. These studies highlight the need for more detailed investigations into the interfacial behavior under dynamic loading conditions.
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Qian Yin, Xinxin Nie, Zhigang Tao, Manchao He, Wenhua Zha, Gang Wang, Zhiqiang Yin, Jiangyu Wu, Linfeng Wang, Yajun Ren (2025). Dynamic mechanical responses and debonding failure mechanisms of a bolt–resin–rock anchoring system subjected to cyclic shear loading. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3161-3
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Frequently Asked Questions
What is the main focus of this study?
This study investigates the mechanical responses and debonding failure mechanisms of a bolt–resin–rock anchoring system under cyclic shear loading, examining the effects of initial normal load, shear displacement amplitude, frequency, and rock type on performance.
How does the initial normal load affect the anchoring system?
Increasing the initial normal load from 7.5 to 120 kN enhances both peak and residual shear loads, with increments ranging from 1.98% to 35.25% for peak and 32.09% to 86.74% for residual loads, indicating improved load-bearing capacity.
What are the typical failure modes observed?
Cyclic shear loading induces anisotropic interfacial degradation, with predominant debonding at the resin–rock interface. The damage severity and failure mode depend on the rock type, with coal governed by coal strength, sandstone by resin–rock bonding, and limestone by resin strength and bolt–resin bonding.
Why is this research important for underground engineering?
Understanding the dynamic behavior and failure mechanisms of anchoring systems under cyclic shear loading is crucial for ensuring the long-term stability and safety of underground structures, such as roadways and tunnels, which are subjected to dynamic disturbances from mining and other activities.
What methods were used in this study?
The study employed systematic experimental analysis, measuring shear load, normal displacement, shear wear characteristics, and strain field evolution under varying conditions of initial normal load, cyclic shear displacement amplitude, frequency, and rock type.
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