Zhuojin Pipe Fitting Co., LtdBearing Capacity and Mechanical Characteristics of Grouting-Filled Steel Tube Piers for Mine Roadway Support
Literature Overview
This 2024 paper by Xie Shuaishuai et al., published in Mining Research and Development, presents experimental and numerical studies on grouting-filled steel tube piers used for roadside support in coal mine roadway preservation. The authors propose substituting traditional concrete with grouting material as the filler for steel tubes (Ф159 mm × 8 mm) to achieve both support resistance requirements and improved construction operability in underground mining environments. The research employed ABAQUS finite element analysis alongside physical testing to evaluate bearing capacity and deformation characteristics.
Core Technical Findings
The experimental results demonstrate that grouting-filled steel tube piers with a water-to-grout ratio of 0.4 achieve bearing capacities exceeding 2000 kN, satisfying the requirements for roadside support in coal mine roadways and other engineering applications. Key observations from the study include:
| Parameter | Value / Observation |
|---|---|
| Steel tube specification | Ф159 mm × 8 mm |
| Grouting material water-to-grout ratio | 0.4 |
| Achieved bearing capacity | > 2000 kN |
| Deformation pattern | Layered folding |
| Maximum deformation location | Mid-section of pier |
| Stress distribution (short column) | Maximum near loading face, uniform at mid-section |
| Stress distribution (long column) | Bending deformation at mid-section |
Deformation and Failure Characteristics
The study identifies several important deformation behaviors:
- Layered folding occurs during loading, with the maximum deformation occurring at the intermediate position of the pier.
- The rib-protected pressure plate structure at the top and bottom exhibits high bearing capacity and effectively maintains pier stability.
- Short column specimens show maximum stress concentrated near the loading face, with uniform stress distribution at the mid-section.
- Long column piers exhibit bending deformation at the intermediate position, requiring consideration of capacity reduction with increasing column length.
Engineering Practice Analysis
From a steel pipe engineering standpoint, this study addresses a critical issue: the interaction between steel tube and internal filler material under compressive loading. The findings have direct relevance to concrete-filled steel tube (CFST) column design in building and process plant construction.
Comparison with Traditional CFST Design
| Aspect | Grouting-Filled Pier | Traditional CFST Column |
|---|---|---|
| Filler material | Grouting slurry (water-grout ratio 0.4) | Ready-mix concrete (C30-C60) |
| Construction method | Pumped injection | Placed and vibrated |
| Curing environment | Underground, confined | Above-ground or accessible |
| Filling quality control | Difficult to verify | Visual and slump testing possible |
| Bearing capacity | > 2000 kN (Ф159 × 8) | Typically higher with denser fill |
| Deformation mode | Layered folding | Local buckling, crushing |
Key Engineering Considerations
The layered folding deformation pattern observed in grouting-filled piers differs from the typical local buckling failure mode of CFST columns. This suggests that the grouting material, while providing adequate bearing capacity, may not develop the same confining pressure on the steel tube wall as hardened concrete. The implications for steel tube design include:
- The steel tube wall thickness (8 mm in this study) must be sufficient to resist the lateral pressure from the grouting material during loading.
- The layered folding pattern indicates potential interface slip between grout and steel tube, suggesting that bond strength may be a governing design parameter.
- For long columns, the bending deformation at mid-section highlights the importance of slenderness ratio in design, consistent with classical column stability theory.
Recommendations for Engineering Application
Based on the study findings, the following measures are recommended for practical application:
- Column length management: When extending pier length in field applications, capacity reduction factors must be applied. Reinforcement at the mid-section or increased steel tube diameter should be considered for long columns.
- Grouting quality control: The water-to-grout ratio of 0.4 appears optimal for the tested configuration. Deviations from this ratio may significantly affect both bearing capacity and deformation behavior.
- Pressure plate design: The rib-protected pressure plate structure proved effective in maintaining stability. This design detail should be preserved in engineering applications.
- Monitoring requirements: Given the confined underground environment, post-installation monitoring of pier deformation should be implemented, particularly for columns exceeding the tested length range.
Study Insights and Implications
This research demonstrates a practical innovation in steel tube structural applications by substituting traditional concrete with pumpable grouting material. The key insight for steel pipe engineers is that the mechanical behavior of filled steel tubes is highly dependent on the filler material properties and the bond quality at the steel-fill interface. The layered folding failure mode, while acceptable for the specific application of mine roadway support, would not be suitable for applications requiring strict dimensional stability. The study validates the feasibility of grouting-filled steel tube piers for specific engineering needs while highlighting the importance of understanding failure mechanisms for safe design application. The approach of using pumpable fillers also opens possibilities for repair and retrofitting of existing steel tube structures in difficult-to-access locations, which is particularly relevant for aging pipeline infrastructure.