Key Techniques for the Ultra-Deep Large Flood Diversion Pipeline: A Case Study of Jinshui River Flood Diversion Project in Zhengzhou

The implementation of large-diameter flood diversion pipelines in urban areas serves as an effective strategy to address urban waterlogging issues, which can enhance the resilience of cities to a certain extent against extreme precipitation events. This case study delineates the Zhengzhou Jinshui River flood diversion project, which employs the ultra-large-buried jacking prestressed concrete cylinder pipe (JPCCP), offering a summary and analysis of the pipe design and construction technologies employed in the JPCCP project within collapsible loess stratum, and the study also analyzes the pull-back scheme of the incident involving the front-end sinking of the machine head. Through on-site monitoring experiments, the variation patterns of contact pressure and slurry pressure of large-diameter JPCCPs were analyzed. The results demonstrate that the trends in contact pressure and slurry pressure exhibit a general consistency. During the jacking process, the pressure around the pipe can be categorized into three distinct phases based on grouting frequency or pressure, with notable variations in the pipe–soil–slurry contact state. The difference between the contact pressure and slurry pressure (termed as effective soil pressure) serves as a more accurate method for determining the pipe’s operational state. Moreover, the effective earth pressure at the pipe top demonstrates a higher degree of consistency with the calculation results prescribed by the standards ATV A161 and ASCE 27.