Key Takeaways & Executive Findings
- •• Structural plane dip angle significantly influences the bearing capacity and failure modes of anchorage bodies, with peak stress decreasing from 54.80 MPa to 19.65 MPa as dip angle increases from 0° to 45°. • Bolt anchoring enhances bearing capacity by up to 153.22% at 45° dip angle and transforms failure from brittle to ductile, improving overall stability. • Pull-out tests identify two failure modes: slip at the bolt-rock interface and bolt fracture, with bolt fracture occurring at 45° under a 14.55 kN load, matching the bolt's yield strength. • The failure mechanism involves structural plane sliding that shears the bolt and mechanical interlocking that restricts pull-out, providing insights for support design in complex geological environments.
Abstract
With increasing mining depth in metal mines, the stability of roadway support structures is significantly affected by the complex surrounding rock. This study performs biaxial compression and bolt pull-out experiments on anchorage body specimens with different structural plane dip angles to explore failure mechanisms of anchorage structures and evolutionary law of bolt anchorage force. Results show the dip angle notably impacts the bearing capacity and failure modes of anchorage specimens. Their peak stress exhibits a V-shaped trend: decreasing from 54.80 MPa to 19.65 MPa as dip angles increase from 0° to 45°, with failure mode transitioning from tensile to shear; at 60°, it becomes a tensile-dominated mixed mode. Bolt anchoring significantly enhances bearing capacity (most remarkably by 153.22% at 45°) and changes failure from brittle to ductile. Pull-out tests reveal two failure modes: slip at the bolt-rock interface and bolt fracture. At 45°, bolt fracture occurs under a 14.55 kN peak pull-out load, matching the bolt's yield strength. This failure mechanism involves two key factors: structural plane sliding that shears the bolt, and mechanical interlocking that restricts pull-out, substantially increasing anchorage force. These findings provide insights for stability assessment and support design of roadway structures in complex geological environments.
1. Introduction
As mineral resource consumption and mining scale continue to increase, mineral extraction is gradually shifting towards deeper regions. Many mines are subjected to challenging mining environments where high in-situ stress and high water pressure coexist, along with fractured surrounding rock structures [1−3]. The stress path within the deep rock mass of the mine becomes increasingly complex, with more intense changes. In the production process, the instability of the roadway caused by insufficient support occurs frequently [4, 5]. Among the various factors affecting the stability of the roadway surrounding rock support structures, the parameters of the structural planes are one of the key factors determining the stability in deep rock mass [6, 7]. Thus, how to reasonably design and optimize the support structure under such complex conditions to effectively control the deformation and failure of the surrounding rock has become a critical technical issue that needs to be solved in deep mining.
Anchoring technology, as an efficient support method, has been widely studied and applied in recent years. Anchoring can alter the mechanical properties of rock mass, delaying or inhibiting damage caused by compression, impact, or shear loads on the rock mass [8, 9]. To study the mechanical characteristics of anchorage rock mass under loading, some scholars have conducted research through laboratory experiments and numerical simulations. ZHAO et al [10] performed uniaxial compression tests on rock samples with 45° inclined double-joint through anchors and unanchored specimens. They found that the failure mode of the anchorage double-joint rock mainly involved fracture instability, which can be divided into five stages: sliding of the joint fill, crack caused by joint surface displacement, cracking at the bottom of the rock, crack propagation in the upper rock, and crack penetration. YU et al [11] used coal-rock composite anchor bodies for triaxial loading tests, revealing that the bolts could improve the strength of the structural plane of the composite anchor bodies and limit relative deformation between coal and rock. CHEN et al [12] studied the shear characteristics of anchorage rock joints under different surface roughness conditions and found that bolts effectively limit the sliding of the joint plane, thus enhancing the shear stiffness of the joint specimens. WU et al [13] conducted dynamic Brazilian splitting tests on anchorage specimens made of red sandstone, studying the dynamic tensile properties and failure modes of anchorage specimens. LI et al [14] used a Hopkinson bar to investigate the impact failure response of anchorage specimens under different pretightening forces, concluding that increasing the pretightening force of the bolts could improve the dynamic load-bearing capacity of the anchorage specimens. WU et al [15] studied the dynamic response of anchorage rock mass under lateral im...
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GENG Yi, LI Xi-bing, CHEN Jiang-zhan, ZHAN Xin-yu, YAN Rong-yun, ZHOU Xiao-li (2026). Mechanical behavior and tensile bearing performance of anchorage body under the influence of structural plane dip angle. Journal of Central South University. https://doi.org/10.1007/s11771-025-6108-y
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Frequently Asked Questions
What is the effect of structural plane dip angle on the bearing capacity of anchorage bodies?
The dip angle significantly affects the bearing capacity. As the dip angle increases from 0° to 45°, the peak stress decreases from 54.80 MPa to 19.65 MPa, showing a V-shaped trend. At 60°, the failure mode becomes a tensile-dominated mixed mode.
How does bolt anchoring improve the mechanical behavior of anchorage bodies?
Bolt anchoring enhances the bearing capacity by up to 153.22% at a 45° dip angle and changes the failure mode from brittle to ductile, thereby improving the overall stability of the support structure.
What are the failure modes observed in bolt pull-out tests?
Two failure modes were identified: slip at the bolt-rock interface and bolt fracture. At a 45° dip angle, bolt fracture occurred under a peak pull-out load of 14.55 kN, which matches the bolt's yield strength.
What is the significance of this study for deep mining engineering?
The findings provide insights into the failure mechanisms of anchorage structures in complex geological environments, aiding in the stability assessment and support design of roadways in deep metal mines.
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