Large-Diameter Steel Pipe Jacking Construction Technology for Underground Space Development

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 for large-diameter steel pipe jacking used in the tube-shield pre-built method for underground space construction. This research is supported by the National Natural Science Foundation of China (Project No. 51678226) and provincial-level research programs. The study focuses on the technical characteristics, construction workflow, operational methods, quality control measures, and surveying and correction techniques specific to large-diameter steel pipe jacking operations.

Technical Characteristics and Construction Workflow

Large-diameter steel pipe jacking is a critical construction technique in the tube-shield pre-built method (also known as the box-tube method), where large steel pipe segments are jacked through the ground to form a continuous underground structure. The technique is particularly suited for constructing underground passages, utility tunnels, and transit connections in urban environments where open-cut excavation is impractical.

The construction workflow follows a sequential process: site preparation and shaft construction, pipe segment fabrication and inspection, jacking machine assembly, sequential pipe jacking with intermediate thrust frames, pipe joint welding and sealing, and final structural connection. Each stage requires careful planning and precise execution to ensure structural integrity and geometric accuracy.

Quality Control and Correction Techniques

The quality control framework for large-diameter steel pipe jacking addresses multiple risk factors inherent in the construction process. The primary concerns include pipe ovality deviation, cumulative alignment error, joint leakage, and structural deformation during jacking.

Surveying and alignment control is paramount. The system employs a combination of total station surveying, laser guidance, and internal alignment sensors to monitor pipe position in real time. The allowable cumulative deviation is typically limited to 1/1000 of the jacking distance, with a maximum absolute deviation of 50 mm for pipes with diameters exceeding 4,000 mm. When deviation exceeds the tolerance threshold, corrective measures must be implemented before continuing jacking.

Ovality correction is a critical challenge for large-diameter steel pipes. During jacking, the pipe experiences both axial compressive loads and lateral earth pressure, which can cause the circular cross-section to deform into an oval shape. The allowable ovality is generally limited to 1% of the nominal diameter. Correction methods include:

1. Internal ring stiffeners welded to the pipe interior at regular intervals (typically every 1.5 to 2.0 m).
2. External support rings installed at intermediate thrust frame locations.
3. Controlled jacking force distribution to minimize differential loading.
4. Post-jacking hydraulic correction using internal expansion devices if ovality exceeds tolerance.

Joint integrity is ensured through a combination of butt-welded joints with full-penetration welds and external sealing gaskets. The welding process must comply with applicable standards (GB/T 985, SY/T 0413) and include 100% visual inspection, magnetic particle testing (MT), and ultrasonic testing (UT) for all welds. Hydrostatic pressure testing is performed at intervals to verify joint watertightness.

Engineering Practice Considerations

From an engineering practice perspective, several factors deserve special attention during large-diameter steel pipe jacking construction:

• Thrust frame design: The intermediate thrust frames must be designed to withstand the cumulative jacking force plus a safety factor of 1.5 to 2.0. Frame spacing is determined by the maximum allowable compressive stress in the pipe wall, typically limited to 0.6 times the yield strength.
• Ground treatment: In soft ground conditions, grouting ahead of the jacking face reduces friction resistance and stabilizes the excavation. The grouting pressure should be controlled to avoid ground heave or settlement.
• Pipe segment fabrication: Large-diameter steel pipes are typically fabricated as spiral-welded or longitudinally welded segments. The welding procedure must be qualified per WPS/PQR, and welders must hold valid certifications. Pre-weld heat treatment may be required for pipe wall thicknesses exceeding 25 mm.
• Safety management: The confined space nature of the jacking operation requires strict adherence to safety protocols, including adequate ventilation, continuous gas monitoring, emergency evacuation procedures, and restricted access to the jacking area.

Study Insights and Reflections

This study provides a comprehensive framework for the construction technology of large-diameter steel pipe jacking, which is a specialized application that bridges the fields of steel pipe engineering, geotechnical engineering, and construction management. The integration of surveying precision, structural engineering, and welding quality control into a unified construction methodology is essential for successful project delivery. Engineers should note that the success of this technique depends not only on the structural adequacy of the steel pipe but also on the precision of the construction process, particularly the control of alignment and ovality deviations. The lessons learned from this research are directly applicable to similar underground construction projects involving large-diameter steel pipe installation.