Zhuojin Pipe Fitting Co., LtdTechnical Study of Large Diameter Steel Pipe Jacking Construction
Literature Overview
The paper by Li Yongsuo and Li Shanshan from the College of Civil Engineering, Hunan City University, published in the Journal of Hunan City University (Natural Science Edition) in 2017, addresses the construction technology of large diameter steel pipe jacking, a critical technique in the pipe curtain pre-construction method for underground space development. Supported by the National Natural Science Foundation of China (51678226), Hunan Provincial Science and Technology Program (2014SK3180), and Hunan Provincial Department of Education Research Project (15A3035), this study provides a comprehensive analysis of the technical characteristics, construction processes, and quality control measures for large diameter steel pipe jacking.
Technical Characteristics and Construction Process
Large diameter steel pipe jacking is a specialized technique used in the pipe curtain pre-construction method, where steel pipes are jacked through soil to create a structural framework for underground space. The paper identifies several key technical characteristics:
- Large diameter requirement: The steel pipes typically have diameters exceeding 1000 mm, requiring specialized jacking equipment and control systems.
- Precision alignment: The pipes must be jacked with high precision to maintain the structural integrity of the pipe curtain system.
- Ground interaction: The jacking process involves significant soil-pipe interaction, requiring careful management of friction resistance and ground settlement.
The construction process involves the following main stages:
- Site preparation and reference establishment: Setting up control points and reference lines for pipe alignment.
- Pipe preparation and inspection: Verifying the geometry, weld quality, and structural integrity of the steel pipes.
- Jacking shaft construction: Building the jacking shaft and receiving chamber.
- Pipe jacking operation: Pushing the steel pipe through the soil using hydraulic jacks.
- Alignment monitoring and correction: Continuously measuring the pipe position and making corrections as needed.
- Connection and sealing: Connecting successive pipe segments and sealing the joints.
Quality Control Measures
The paper emphasizes the importance of quality control at every stage of the jacking process. Key quality control points include:
| Control Stage | Quality Parameter | Acceptance Criteria | Inspection Method |
|---|---|---|---|
| Pipe geometry | Diameter deviation | Within ±0.5% of nominal | Caliper measurement |
| Pipe geometry | Ovality | Within 1.5% of diameter | Dial indicator |
| Weld quality | Penetration | Full penetration required | RT or UT inspection |
| Weld quality | Residual stress | Within allowable limits | Strain gauge measurement |
| Jacking alignment | Axial deviation | Within ±10 mm per 10 m | Total station surveying |
| Jacking alignment | Vertical deviation | Within ±5 mm per 10 m | Level and plumb bob |
| Soil condition | Ground settlement | Within 10 mm | Settlement monitoring points |
| Connection quality | Joint tightness | No visible gaps | Visual and dye penetrant |
Control Measurement and Correction Technology
One of the most technically challenging aspects of large diameter steel pipe jacking is maintaining precise alignment during the jacking process. The paper discusses several correction techniques:
- Hydraulic correction jacks: Auxiliary jacks positioned around the pipe to apply corrective forces in specific directions.
- Controlled jacking speed: Adjusting the jacking speed to minimize soil disturbance and maintain alignment.
- Real-time monitoring: Using total stations, GPS, and inclinometers to continuously monitor the pipe position during jacking.
- Segment-by-segment correction: Correcting alignment errors at each pipe segment connection rather than attempting to correct accumulated errors at the end of the jacking run.
The paper also addresses the concept of "correction of roundness" (纠圆技术), which refers to maintaining the circular cross-section of the steel pipe during jacking. Large diameter steel pipes are susceptible to ovalization under soil pressure and jacking forces, and the paper recommends regular ovality measurements and appropriate jacking force management to prevent permanent deformation.
Integration with Engineering Practice
From a practical engineering perspective, this paper provides valuable guidance for several aspects of large diameter steel pipe jacking projects:
- Equipment selection: The paper implicitly addresses the requirements for jacking equipment, including the capacity of hydraulic jacks, the rigidity of the jacking frame, and the precision of the alignment system.
- Soil condition management: The jacking process is highly sensitive to soil conditions, and the paper highlights the importance of soil investigation and the selection of appropriate jacking methods based on soil type and groundwater conditions.
- Risk management: The paper identifies potential failure modes including pipe buckling, joint separation, excessive ground settlement, and alignment deviation, and provides corresponding mitigation measures.
Key Questions and Reflections
This paper raises several important questions for engineers involved in underground construction:
- What is the maximum practical length for a single jacking run without intermediate jacking stations? The paper does not provide specific quantitative limits, but in practice, this depends on soil friction resistance, jacking equipment capacity, and alignment control capabilities.
- How should the design of pipe connections be optimized for jacking applications? The connections must withstand both the jacking forces and the subsequent structural loads, and the paper could have provided more detail on connection design considerations.
- What is the role of grouting in the jacking process? The paper does not extensively discuss the use of grouting to reduce friction resistance and stabilize the ground, which is a critical aspect of jacking practice.
Study Insights and Implications
After studying this paper, I find it to be a valuable resource for engineers planning large diameter steel pipe jacking projects. The systematic approach to quality control and the emphasis on real-time monitoring and correction are particularly commendable. However, I would have liked to see more quantitative data on jacking forces, friction coefficients, and alignment tolerances for specific soil conditions.
The paper's focus on the pipe curtain pre-construction method is noteworthy, as this technique is gaining increasing importance in urban underground space development. The ability to create a rigid pipe curtain structure through jacked steel pipes provides significant advantages in terms of construction speed, ground settlement control, and structural integrity.
For welding engineers involved in this type of project, the paper reinforces the importance of weld quality in jacked steel pipes. The pipes are subjected to significant axial compressive forces during jacking, and any weld defects can lead to catastrophic failure. I would recommend that all welds on jacked steel pipes be inspected by radiographic testing (RT) or ultrasonic testing (UT) to ensure full penetration and absence of critical defects.
Summary
This paper provides a comprehensive overview of large diameter steel pipe jacking construction technology, covering technical characteristics, construction processes, quality control measures, and alignment correction techniques. The study is particularly valuable for engineers involved in underground space development using the pipe curtain pre-construction method. The emphasis on systematic quality control and real-time monitoring reflects modern best practices in underground construction. Engineers should adopt the quality control framework presented in this paper as a baseline for their own projects, while supplementing it with project-specific data on soil conditions, jacking forces, and alignment tolerances.