Working hard to achieve our mission | The two lines of the pipe jacking section of the Xutao Road to Hengshan Road tunnel project were successfully connected

On January 12, as the "Grand Canal" ultra-large-section rectangular pipe jacking machine slowly spun out on the east bank of the canal, the pipe jacking section of the southern line of the Xutao Road-to-Hengshan Road tunnel project was successfully connected. Since then, the pipe jacking work of the Xutao Road to Hengshan Road tunnel project, which was implemented by the Suzhou Municipal Housing and Urban-Rural Development Bureau, has been completed.

The northern line of the tunnel started jacking on June 18, 2021, and was successfully connected on September 15, 2021; the southern line of the tunnel started jacking on October 30, and the two lines were connected on January 12, 2022. The completion of the double-line tunnel has laid a solid foundation for the entire project to be completed and opened to traffic. In the next step, the Xutao Road-to-Hengshan Road tunnel project will be fully transferred to the construction of the remaining exposed and buried sections, the back section after pipe jacking, and ancillary works.

Project overview

The Xutao Road-to-Hengshan Road tunnel project starts from the tunnel grounding point at the intersection of Xinyuan Road on the east side of Binhe Road, extends eastward along Hengshan Road, and bifurcates through the Beijing-Hangzhou Canal. The northern tunnel connects to Xutao Road, with a total length of about 896 meters; the southern tunnel connects to Zaoshi Street, with a total length of about 1,293 meters. Construction officially started at the end of December 2018, and is scheduled to be completed by the end of 2022. After the completion of the project, it will greatly alleviate the traffic pressure across the Beijing-Hangzhou Grand Canal between Suzhou District and the Hi-tech Zone, further improve the urban road network structure in the southwest region of Suzhou's central urban area, and effectively divert the traffic flow of surrounding elevated roads.

Implementation significance

This project is not only a livelihood project to ensure travel, but also has the mission of protecting the Beijing-Hangzhou Grand Canal, a world cultural heritage. Therefore, the non-excavation method of rectangular pipe jacking construction is used to allow the channel to operate normally during the entire jacking process, while avoiding damage to the water quality environment of the Grand Canal, so that the intangible cultural heritage and historical features of the Beijing-Hangzhou Grand Canal can be effectively protected.

Construction difficulty

     This project is not only the first tunnel under the Beijing-Hangzhou Grand Canal in Suzhou, but also the first time in China that a large-section, long-distance rectangular pipe jacking method is used to penetrate the urban trunk road of the Beijing-Hangzhou Grand Canal. Due to the long-distance crossing of the main channel, the shallow overburden of the river jacking, and the settlement of the wading bottom Construction difficulties such as control, and due to complex geological and hydrological conditions, there is a possibility that the river bed will penetrate and form a funnel, causing water seepage in the machine head or pipe sections, or even water and sand intrusion from the working well. Its construction difficulty, section size and jacking length are the highest in domestic rectangular pipe jacking municipal vehicle tunnels.

Technical support

To successfully implement this "super project", the project builder has invited academicians of the Chinese Academy of Engineering and authoritative domestic underground engineering experts to optimize the project design plan. Through BIM technology simulation modeling, 33 construction drawings have been optimized and more than 300 construction plans have been improved. In order to improve the construction quality, the project uses the first 10 meters of jacking as a test section to comprehensively analyze data such as jacking construction parameters to ensure that the attitude of the pipe jacking machine is accurate and does not yaw; in order to solve the problem of huge friction during long-distance jacking, drag-reducing mud was prepared for the test, and drag-reducing mud and thick mud were injected outward from the grouting holes to form a mud sleeve around the pipe section, reducing the friction between the pipe wall and the soil, and achieving continuous, balanced, and controllable advancement speed and pipe section installation.

Crossing the Grand Canal is the key to jacking construction. When the pipe top crosses the river, the top soil is only 4 meters, and the crossing area is mostly composed of silt layer, silt layer, and silt layer. Faced with unprecedented technical difficulties, the project carried out research on the subject of "Research on Key Technologies for Construction of Municipal Vehicle Tunnels with Long-Distance Jacking of Rectangular Pipes through a Large Section of the Beijing-Hangzhou Canal Under High Water Pressure and Shallow Burial in Water-rich Sand Soil". It has successively overcome problems such as control of origination and reception risks, shallow covering of soil and high water pressure through the Beijing-Hangzhou Canal, long-distance jacking of large sections to reduce drag, and jacking axis control. A total of 8 patents have been applied for, and 1 software copyright has been applied for.

After the completion of the tunnel project connecting Xutao Road to Hengshan Road, it will effectively open up the "dead end road" between Hengshan Road and Xutao Road, quickly connect Gusu District and the High-tech Zone, greatly facilitate travel and economic exchanges on both sides of the Grand Canal, and contribute to Suzhou's high-quality development to a new level.

(Source: Suzhou Municipal Housing and Urban-Rural Development Bureau)