Seismic Performance Assessment of Water Pipes Retrofit with Corrosion–Protection–Liner Technology

Seismic retrofit of critical underground water pipelines, serving as a key component of lifeline networks, has become an urgent need in engineering practice to improve the performance and serviceability of these critical lifelines. The corrosion protection liner (CPL) technology consists of installing flexible plastic liners with V-shaped anchoring studs inside existing pipelines and subsequently filling cement mortar to the gap between the waterproof liner and the pipeline. With the excellent chemical resistance, impermeability, and fast construction cycles, CPL provides an economic and environmentally friendly alternative for pipeline rehabilitation without large-scale excavation. However, the lack of verification and quantification of the seismic performance of pipelines rehabilitated with CPL remains a critical deficiency for its application as an effective seismic retrofit method for underground pipelines. This study focuses on the response of CPL-strengthened ductile iron (DI) push-on joint by evaluating the liner debonding, relative joint openings produced by axial loadings simulating the seismic loading experienced by the pipeline during an earthquake event. Full-scale quasi-static tests were performed on two water-pressurized DI pipelines with push-on joints before and after reinforcement with the CPL. Moreover, based on the joint response under quasi-static loading, numerical models were developed for capturing the axial behaviors of CPL-reinforced joints that considers strength degradation and energy dissipation. Both the test results and numerical analyses indicate that CPL provides substantial axial strength to the joints of DI pipelines and improve their seismic behavior under high intensity ground motions. But the quality of the heat melting welding of CPL remains a critical uncertain factor, and poor-quality control may be adverse to the seismic performance of the retrofitted pipeline.