Effective identification of damage characteristics and failure modes for buried pipelines subjected to fault movements is crucial for early design and disaster assessment. In the preceding companion paper, the structural responses of large-diameter prestressed concrete cylinder pipeline (PCCP) subjected to fault displacement were initially investigated under the condition where faulting crosses pipe barrel vertically, and the deterioration process and failure modes were summarized. However, the structural responses of jointed pipelines are closely tied to faulting parameters. In this paper, a study on the location and angle of the fault plane is conducted, and the damage response and failure modes of large-diameter PCCPs are analyzed in detail and compared. The results show that strike-slip fault movement causes pipeline movement through pipe-soil interaction, and the fault displacement is accommodated by several pipe segments for the large diameter-to-length ratio PCCPs. When the fault plane crosses the pipe segment at an acute angle, the primary failure modes include material damage to the pipe joints and barrel, as well as the risk of joint leakage. Material damage occurs at the joint when the fault plane passes through the PCCP joint. Given the mechanical properties and seismic resilience of PCCPs, it is advisable to avoid faulting at acute angles crossing pipeline joints. This work focuses on the structural behavior of segmented composited PCCPs crossing a fault, aiming to predict pipeline damage and failure. The findings contribute to a comprehensive understanding of the failure modes, damage characteristics, and disaster evaluation of PCCPs under strike-slip fault conditions.

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.

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.