How is a rectangular pipe jacking machine used in subway projects?

2026-08-30 11:19:32

The rectangular pipe jacking machine has emerged as a transformative technology in subway construction, particularly for underground passages, station entrances, and utility tunnels. Unlike traditional circular pipe jacking machines, rectangular variants offer significant advantages in urban environments where space is constrained and surface disruption must be minimized. The application of rectangular pipe jacking machines in subway projects has grown rapidly across China, with numerous successful implementations in cities such as Beijing, Shanghai, Guangzhou, Shenzhen, Hangzhou, Qingdao, and Zhengzhou.

Primary Applications in Subway Construction

Subway Station Entrances and Exits

One of the most common applications of rectangular pipe jacking machines in subway projects is the construction of station entrances and exits. These structures typically require rectangular cross-sections to efficiently utilize underground space and accommodate pedestrian flow. The rectangular shape allows for more efficient use of the excavated area compared to circular alternatives, reducing the need for additional backfilling and structural modification. The Hefei Rail Transit system, for example, adopted rectangular pipe jacking for its station entrance construction, marking a significant milestone in the city's subway development.

Underground Pedestrian Passages

Subway systems often require underground pedestrian passages to connect different lines, station platforms, or adjacent buildings. Rectangular pipe jacking machines are particularly well-suited for these applications because they can create passages with optimal cross-sectional shapes that match the functional requirements of pedestrian movement. The ability to excavate rectangular tunnels directly eliminates the need for subsequent reshaping of circular tunnels, saving both time and construction costs.

Subway Parking Lines

A particularly innovative application of rectangular pipe jacking technology is in the construction of subway parking lines. In August 2025, the first rectangular pipe jacking machine specifically designed for subway parking line construction was launched in Hangzhou, representing a groundbreaking achievement in this field. The machine was deployed for the construction of underground parking lines in the Hangzhou Rail Transit system, demonstrating the technology's adaptability to specialized subway infrastructure needs. This application was further highlighted at the BICES 2025 exhibition, where the successful implementation of large-section rectangular pipe jacking machines in subway parking line construction was showcased.

Technical Advantages for Subway Applications

Space Utilization Efficiency

The rectangular cross-section of these machines allows for significantly better space utilization compared to circular tunnels. In subway applications, where the usable space must accommodate equipment, ventilation, and pedestrian movement, the rectangular shape provides a more functional envelope. This is particularly important for subway station entrances and underground passages, where the clear width and height must meet specific operational requirements.

Ground Disturbance Minimization

Subway construction in urban environments often occurs beneath existing buildings, roads, and utilities. The earth pressure balance (EPB) mechanism employed by rectangular pipe jacking machines enables precise control of ground settlement, making them ideal for sensitive urban environments. By maintaining balanced pressure at the tunnel face, these machines can effectively manage ground movement and protect surface structures.

Reduced Surface Disruption

Unlike traditional open-cut construction methods, rectangular pipe jacking technology allows for underground construction without extensive surface excavation. This is particularly valuable in congested urban areas where maintaining traffic flow and minimizing disruption to businesses and residents is critical. The non-destructive nature of the pipe jacking process eliminates the need for large-scale trenching and reduces the overall construction footprint.

Notable Project Implementations

Hangzhou Metro Parking Line Project

The Hangzhou Metro project represents a landmark application of rectangular pipe jacking technology in subway parking line construction. The machine launched in August 2025 was specifically designed for this purpose, featuring a large cross-section that could accommodate the space requirements of underground parking facilities. This project demonstrated the feasibility of using rectangular pipe jacking for specialized subway infrastructure beyond traditional tunnel applications.

Qingdao Metro Hard Rock Application

In 2021, Qingdao achieved a significant milestone by deploying a rectangular pipe jacking machine for the first time in hard rock conditions on Metro Line 4. This application demonstrated the technology's versatility and its ability to handle challenging geological conditions commonly encountered in subway construction. The successful implementation in Qingdao expanded the potential use cases for rectangular pipe jacking in subway projects across different geological settings.

Shenzhen and Zhengzhou Large-Section Projects

The world's largest cross-section combined rectangular pipe jacking machine, named "Dayu Excavation Number," was launched in Shenzhen in April 2023. This massive machine, manufactured by China Railway Engineering Equipment Group, was designed for subway-related infrastructure construction. The machine was first下线 in Zhengzhou in January 2023 before being deployed to Shenzhen. This project showcased the capability of rectangular pipe jacking technology to handle extremely large cross-sections, opening new possibilities for subway station and underground space construction.

Operational Process in Subway Construction

Preparation and Launching

The rectangular pipe jacking machine is assembled and lowered into a pre-constructed launching shaft at the designated starting point. The machine is positioned and aligned according to the designed tunnel axis, with all systems tested and calibrated before operation begins. The first pipe section is then connected to the machine, and the thrust system is prepared for the jacking process.

Excavation and Pressure Balance

As the machine advances, its cutterheads excavate the soil at the tunnel face. The excavated material enters the muck chamber, where it is maintained under controlled pressure to balance external earth and water pressures. This earth pressure balance mechanism is critical for maintaining ground stability and preventing surface settlement. The machine's screw conveyor system removes the conditioned soil from the chamber, with the discharge rate carefully controlled to maintain pressure equilibrium.

Pipe Installation and Grouting

As the machine advances, pipe sections are installed behind it, forming the permanent tunnel structure. The annular gap between the pipe and the surrounding ground is simultaneously filled with lubricating and filling grout to reduce friction and provide immediate ground support. This grouting process is essential for minimizing ground settlement and ensuring the long-term stability of the tunnel.

Steering and Alignment Control

Throughout the excavation process, the machine's position and orientation are continuously monitored using guidance systems. Steering jacks allow for precise adjustments to maintain the designed tunnel alignment, ensuring that the finished structure meets the required specifications for subway operations.

Future Development Trends

The application of rectangular pipe jacking machines in subway projects continues to evolve, with several key trends shaping future development. First, the trend toward larger cross-sections is enabling the construction of more spacious underground facilities, including subway station halls and parking areas. Second, the development of machines capable of handling increasingly complex geological conditions, including hard rock and mixed-face conditions, is expanding the technology's applicability. Third, the integration of advanced monitoring and control systems is improving the precision and reliability of rectangular pipe jacking operations, making them suitable for even the most demanding urban environments.

The rectangular pipe jacking machine has become an indispensable tool in modern subway construction, offering significant advantages in space utilization, ground disturbance minimization, and surface disruption reduction. From station entrances and underground passages to specialized parking line facilities, the technology has demonstrated its versatility and effectiveness across a wide range of subway applications. As cities continue to expand their underground transportation networks, the rectangular pipe jacking machine will play an increasingly important role in shaping the future of subway infrastructure development.