Connecting macroscopic mechanical models to micromechanical phenomena in the failure analysis of a large-diameter prestressed concrete cylinder pipeline

• PCCP burst happens after a critical number of prestressing wires fails. • Hydrogen-assisted stress corrosion cracking causes damage propagation. • An analytic model predicts the stress increase after wire breakage. • The model reinforces the conclusions of the root cause failure analysis. Large-diameter prestressed concrete cylinder pipelines for potable water are of crucial importance for many urbanised areas around the world. A failure case in the Cutzamala system (Mexico) was used to analyse the damage propagation leading to catastrophic rupture. At the macroscopic scale, failure is observed as the progressive fracture of prestressing wires. Low magnification observation suggests a mechanism related to fretting and delamination, but detailed scanning electron microscopy shows that hydrogen-assisted stress corrosion cracking is active. A mechanical model was developed, inspired by the shear lag approach for fibre-reinforced composites. The analysis describes the stress redistribution within and between the wires by a separable partial recurrence-differential equation. The analytical solution shows the importance of wire debonding, to determine the stress increase ahead of the crack. The model can be refined in future work as a tool for the prediction of damage propagation under specific environmental, operational and design conditions.