Assessment of Failure Mechanisms of Joints in Ultra-Large Section Jacking Prestressed Concrete Cylinder Pipe (JPCCP): Insights from Zhengzhou, China

Jacking prestressed concrete cylindrical pipe (JPCCP) is an innovative pipe that combines the benefits of prestressed concrete cylinder pipe (PCCP) and the pipe jacking method, playing a crucial role in water conservancy projects across China. Due to its structural characteristics and manufacturing process, the JPCCP joints are prone to circumferential cracks during jacking, and the harmful cracks can damage the inner concrete core over time, posing significant safety risks to the pipeline's structural integrity. To investigate the influence of jacking factors on cracking behavior at the JPCCP joints, this study examines the failure modes of concrete at the bell-spigot ends of the pipes. The analysis combines field experiments and numerical simulations, using data from China's largest diameter JPCCP project. The study finds that local tensile stress at the spigot end is the primary cause of cracking and potential fracture, and micro-cracks initially form on the inner surface of the damaged region, progressing circumferentially. Both the jacking force and deflection angle significantly affect the distribution and magnitude of the maximum principal stress in the concrete. The ultimate jacking forces for deflection angles of 0.1° and 0.5° are 3842 T and 1134 T, respectively. Controlling concrete cracking can be achieved in the construction process by reducing the relative deflection between adjacent pipes. This study introduces novel approaches for improving JPCCP construction techniques and optimizing joint design, providing valuable insights for future projects.