Prestressed concrete cylinder pipes (PCCPs), which are composite pipes, are widely used in cross-basin water transfer projects and urban underground pipe network construction owing to their low cost, long life, high pressure-bearing capacity, and ease of construction and installation. However, in the course of long-term service, PCCPs may undergo damage and fail to different degrees due to the combined effect of external loads, ion erosion in the soil, and uneven settlement of the foundation. Hence, long-term monitoring is essential for the safety evaluation and risk assessment of pipelines. In this study, a prototype centralized filament-breaking damage test was performed on a large-diameter embedded PCCP with an inner diameter of 3.4 m and a length of 5 m, revealing a correlation between the number (proportion) of broken filaments and the extent of PCCP damage. The results showed that the maximum wire breakage ratio of the PCCP specimen was approximately 20% under the design internal pressure. Meanwhile, a safety monitoring method for PCCPs was established based on distributed acoustic sensing, which helps monitor destructive events, such as wire breakage and retraction, and cracking of the mortar protective coating and core concrete during PCCP operation. Moreover, the vibration signal pattern was analyzed, and its characteristics were deciphered, providing a new means of monitoring the long-term operational safety of PCCPs and providing early warning.

Uniform support from the surrounding soil is important for maintaining the stable operation of buried pipelines. For segmented prestressed concrete cylinder pipe (PCCP), localized soil voids around the joint due to leakage or engineering activities make the pipe unsupported partially and threaten its integrity and strength. In this paper, the impact of a localized soil void on a pipe joint is qualitatively assessed using a beam-on-elastic-spring approximation model. It further provides quantitative analysis through a nonlinear finite element (FE) model of PCCPs and the surrounding soil. The derived algebraic solutions indicate that a unilateral local void induces shear force and rotation at the joint, whereas shear force becomes negligible when the void spans the joint, leading to increased rotation. Moreover, the rotation angle shows a positive correlation with soil load and a negative correlation with pipe diameter. Numerical analysis reveals that void elongation along the pipe length has a more pronounced effect on structural response than void depth and angle. When the void length reaches 2.5 m, the maximum principal stress on the mortar layer of the PCCP increases approximately eight-fold compared to the scenario without voids. Due to the rigidity and safety factor of the PCCP, small voids in the bedding typically do not cause immediate pipe damage or joint leakage; however, they can significantly alter the stress distribution within both the pipe and surrounding soil. As the void develops, the soil may collapse and compromise support, leading to additional secondary disaster risks and potential threats to pipeline safety. This research emphasizes the importance of effective pipe-soil interactions and provides theoretical insights for developing repair strategies for PCCP.

The buried prestressed concrete cylinder pipe (PCCP) in mountainous areas easily suffers from geological disasters such as falling rocks, which result in leakage, pipe explosion and other structural safety issues. According to engineering practice, a rock-soil-pipe finite element model of buried PCCPs impacted by spherical falling rocks is established in this paper. The PCCP structural response to the impacts of falling rocks under different parameter settings is calculated. Taking the maximum plastic damage value of PCCP concrete cores as the evaluation index, an intelligent evaluation model of PCCP structural safety under falling rock impacts is built based on the Bayesian Optimization-Long Short-Term Memory (BO-LSTM) model. The constructed model is used to quickly predict the damage caused by falling rocks to the PCCP structure after the disaster. Meanwhile, the model provides support for the implementation of subsequent engineering measures. The study results show that the BO-LSTM-based intelligent evaluation model can accurately predict the PCCP structural damage caused by falling rock impacts, and it has practical application value.

Strengthening interconnection and interoperability between water supply groups and reservoirs in super mountainous cities, a large number of water conveyance tunnels need to be built. Jacking prestressed concrete cylinder pipe (JPCCP) has been applied to pipe jacking construction in soil stratum. A new type of JPCCP was proposed to meet the needs of long-distance pipe jacking construction of water conveyance tunnels in rock stratum. However, the frictional resistance of the rock mass-pipe interface is very complicated in engineering practice. It is common for pipe sections to become stuck due to the excessive friction. The mechanical response and deformation characteristics of the new JPCCP when pipe sticking problem occurred have attracted more and more attention. In this paper, the characteristics of concrete strain, steel stress, crack propagation and axial stress transfer under axial jacking force were studied by the combined method of fullscale test and numerical simulation. The full-scale tests results showed that the concrete internal strain and surface strain of the pipe increased with the increase of the axial jacking force. The spigot end was the weakest area, where cracks appeared first and then developed along the circumferential direction in the full-scale tests. The potential causes of pipe cracking in full-scale tests were carefully discussed. It is suggested to improve the mechanical performance of the spigot end. Finally, the numerical simulations further revealed the axial stress transfer characteristics of the new JPCCP.