On April 12, as the final pipe section was precisely positioned, good news came from Construction Section B2 of the Yujiang South Trunk Line of the Guangxi Beibu Gulf Water Resources Allocation Project: the special pipe-jacking works at the crossing with the Luzhai-Qinzhou Port Expressway were successfully completed. Under complex geological conditions, the project successfully crossed beneath the bridge of the expressway under construction with millimeter-level precision, achieving "zero disturbance" to the bridge pile foundations, overcoming another key technical challenge at a critical node, and clearing an important obstacle for the full-line advancement of this national water network backbone project.

This pipe-jacking operation is located at the key intersection of the Yujiang South Trunk Line and the Luzhai-Qinzhou Port Expressway, where the water transmission pipeline must pass beneath the bridge of the expressway under construction. The geological conditions in the construction area are extremely complex: the upper layer consists of highly fractured, strongly weathered siltstone up to 10 meters thick, while the lower layer consists of residual soil or completely to strongly weathered siltstone with poor self-stability and developed fissures.

How to ensure the absolute safety of the pile foundations of the expressway bridge above during the tunneling process became the greatest challenge facing the project.

To ensure project safety, the construction unit organized all participating parties to conduct repeated demonstrations and ultimately determined a refined construction plan of "dual-pipe jacking, consolidation before excavation."

Before construction, the project team carried out grouting reinforcement of the soil between the pipeline and the bridge piles, creating a solid "isolation barrier" that effectively blocked the transmission of construction disturbance to the pile foundations. At the same time, cement mixing piles were used to reinforce the soil in the portal area of the working shaft, significantly improving the stability and impermeability of that area and providing reliable assurance for the safe launch of the pipe-jacking machine.

During tunneling, the project team adopted an advanced rock pipe-jacking machine. The equipment integrates an intelligent control system and high-precision guidance technology, enabling precise operation and real-time deviation correction. Its full-face panel cutterhead and secondary crushing device can efficiently break complex rock strata, and with a multi-port slurry inlet design, it can flexibly handle alternating soft and hard ground, ensuring smooth muck discharge and minimizing disturbance to the surrounding strata.

After a month of continuous effort, the two pipe-jacking lines achieved a cumulative jacking length of 88 meters and were successfully completed. Monitoring showed that the bridge pile foundations were not disturbed at all during construction, and the accuracy of the jacking axis was strictly controlled within 10 millimeters, achieving an extremely high construction quality standard.

Source: Guangxi Daily