Validating Structural Performance of Internal Replacement Pipe for Legacy Pipelines: Comparison of Tensile Coupon and Full-Scale Test Results

Underground pipelines experience a variety of loading scenarios over their design life, such as deformation from adjacent excavation and traffic-induced loading. Given their age, potential corrosion, and fracture susceptibility, legacy pipelines such as cast iron (CI) are particularly vulnerable to ground movements and are therefore commonly in need of internal rehabilitation to extend their service life. While a variety of internal replacement pipe (IRP) technologies (e.g., cast-in-place pipe, spray-in-place pipe, and others) have various advantages depending on the intended application and deposition method, any current or future system must be capable of accommodating ground movement expected to be imposed over their intended service life. This study explores the mechanical response of rehabilitated pipelines, particularly at critical points like circumferential cracks and joints, to ensure successful design and enhanced performance of internal repairs by assessing material and full-scale test results. It addresses the axial behavior of full-scale, 12-in. (305-mm) diameter specimens. Specimen features a nominal 0.5-in. (13-mm) fully circumferential host pipe gap, simulating a weak joint or crack due to deterioration. Other variables such as the host pipe material and gap opening size were kept constant through tests to ensure the comparability of results. The full-scale test data provided a better understanding of the internal replacement pipe (IRP) behavior compared to the material properties reports from the manufacturer, showing consistency between the coupon test results and the full-scale test results. The results indicate that the stiffer rehabilitation material reached higher stress levels at the early stages of loading, influenced by the material's elastic modulus. Additionally, the performance of unbonded liners in terms of axial deformation demonstrated a lower amount of plastic (residual) deformation. This research contributes to optimizing IRP for a variety of applications and maintaining the long-term mechanical performance of critical buried infrastructure. Moreover, the standardized testing procedures developed can be applied across various rehabilitation technologies, establishing robust and systematic performance metrics.