The Effects of Secondary Pre-Tightening of the Clamping Cable Nodes on Yielding U-Shaped Steel Supports for Use in Deep Soft Rock Roadways
Secondary pre-tightening of clamping cable joints can effectively improve the load-bearing performance of U-shaped steel supports. However, the underlying mechanism of secondary pre-tightening has remained a critical knowledge gap in ground control engineering, and its design still relies on empiric...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Applied Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3417/15/7/3803 |
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| Summary: | Secondary pre-tightening of clamping cable joints can effectively improve the load-bearing performance of U-shaped steel supports. However, the underlying mechanism of secondary pre-tightening has remained a critical knowledge gap in ground control engineering, and its design still relies on empirical approaches without theoretical guidance. To address these challenges, this study proposes a novel mechanistic framework integrating mathematical modelling, experimental validation, and parametric analysis. Specifically, a first-principle-based mathematical expression for the slip resistance of clamping cable joints under secondary pre-tightening was derived, explicitly incorporating the effects of bolt torque and interfacial friction; and a dual-phase experimental protocol combining axial compression tests and numerical simulations was developed to systematically quantify the impacts of initial pre-tightening torque, secondary pre-tightening torque (T<sub>2</sub>), and the timing of secondary pre-tightening (u/u<sub>max</sub>). Three groundbreaking thresholds were identified, as follows: critical initial pre-tightening torque (T<sub>1</sub> > 250 N·m) beyond which secondary pre-tightening becomes ineffective (<5% improvement); minimum effective secondary pre-tightening torque (T<sub>2</sub>/T<sub>1</sub> > 1) for significant load-bearing enhancement; and the optimal activation window (u/u<sub>max</sub> < 50%) balancing capacity gain (<10%) and deformation control. These findings establish the first quantitative design criteria for secondary pre-tightening applications, transitioning from empirical practice to mechanics-driven optimization. |
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| ISSN: | 2076-3417 |