For years, heavy rainfall during the flood season has caused frequent waterlogging on major roads across Weinan, Shaanxi Province, disrupting traffic and daily life. This long-standing urban challenge is now set to be effectively resolved.
On May 31, the final section of pipe-jacking works was successfully completed, marking the full breakthrough of the Zhanbei Street Flood Diversion Channel Project, a key public welfare infrastructure project in Weinan undertaken by The First Engineering Bureau of CREC. With the completion of the main construction works, the project is now entering its final stages before being commissioned.
The project extends 3,723 meters from Hanma Pond in the west, following Channel No. 3 and Zhanbei Street eastward to the western bank of the You River. It comprises 15 sections, including one open channel section, one box culvert section, and 13 flood-diversion pipeline sections constructed using pipe-jacking technology. The pipelines have a diameter of 3,000 millimeters and reach a maximum burial depth of 24.13 meters.
Designed with a maximum flood-diversion capacity of 26 cubic meters per second, the project will raise Weinan’s urban flood protection standard to withstand a once-in-50-years flood event. Upon completion, it will help achieve the goal of preventing floodwaters from entering the city, safeguard the lives and property of approximately 700,000 residents in Linwei District, and contribute to the improvement of the urban ecological environment.
Engineering Through Soft Ground: Overcoming Challenging Soil Conditions
Zhanbei Street is located in Weinan’s older urban district, where underground utility networks are densely distributed and many pipelines have experienced long-term leakage due to age and deterioration. Combined with continuous runoff recharge from the surrounding plateau, the area contains an unusually abundant groundwater system. The construction site is situated on a third-level river terrace, where saturated soft loess deposits reach depths of up to 15 meters. Characterized by high moisture content, large pore spaces, low permeability and strong sensitivity to disturbance, these soil conditions posed significant risks of mud inrushes, water ingress and ground collapse during excavation and tunneling operations.
According to Zhao Jing, Commander of The First Engineering Bureau of CREC’s Weinan Project Command Center, excavation works encountered multiple challenges, including soil collapses between retaining piles, water and mud inflows through shaft walls, seepage and localized ground settlement. The project team successfully stabilized conditions through a combination of counter-pressure backfilling, sleeve-valve grouting, steel pipe grouting, enhanced water-stop curtains and localized dual-liquid grouting treatments, ensuring the safe completion of excavation and foundation sealing operations.
To address the challenges posed by collapsible loess formations, the project team optimized construction methods based on site-specific conditions. Ground grouting and cement mixing piles were used extensively to strengthen and improve soil stability. During construction of the Y8–Y7-1 section, where repeated incidents of ground settlement, surface cracking and tunneling machine displacement occurred, high-pressure jet grouting and cement mixing piles were deployed to reinforce the surrounding soil. In addition, the team replaced the conventional slurry-balance pipe-jacking method with a more suitable earth-pressure-balance technique, precisely controlling chamber pressure, tunneling speed, excavated material volume and synchronous grouting parameters to minimize settlement risks and ensure safe construction.
Navigating a Web of Utilities Beneath the City
Running through the heart of the city, the flood-diversion channel passes beneath a dense network of communication, power, gas, military, water supply and stormwater pipelines. To prevent accidental damage to these critical utilities, the project team established a comprehensive utility detection and protection system.
A dedicated utility investigation team conducted grid-based surveys at 0.5-meter intervals to accurately map underground infrastructure. The team coordinated closely with seven utility owners, including gas, electricity and telecommunications providers, sharing records and conducting verification excavations. Advanced technologies such as pipeline gyroscopes and robotic inspection systems were also deployed to accurately identify underground conditions and establish a robust foundation for safe construction.
Zhanbei Street is one of Weinan’s main urban thoroughfares, lined with densely packed masonry buildings, some located as close as seven meters from construction shafts. Controlling construction-induced disturbances therefore became a major challenge. To address this issue, the project team prepared dedicated construction plans and emergency response procedures in advance, implemented comprehensive monitoring throughout the construction process, and efficiently carried out safety assessments, risk analyses, utility repairs, ground reinforcement and emergency management measures. These efforts minimized impacts on surrounding structures and ensured the project remained both a safe and community-focused undertaking.
Facing complex geological conditions, dense underground utilities and demanding proximity constraints, the builders of The First Engineering Bureau of CREC overcame challenge after challenge through meticulous planning, technical innovation and unwavering commitment.
With the successful completion of this major construction milestone, the project team will accelerate subsequent works, including watertightness testing, pipeline acceptance procedures and road restoration. The goal is to bring the project into operation as soon as possible, further enhancing flood resilience, protecting lives and property, and strengthening the safety of Weinan’s urban transportation network during future flood seasons.
