Experimental study of the separated joint of an underground pipeline rehabilitated by cured-in-place pipe

Abstract

Reinforced concrete pipes (RCPs) were commonly used in older underground pipelines in Taiwan, China. However, their joints are prone to damage, including fracture and separation, from problems such as overloading, poor backfilling, and liquefaction. For the rehabilitation of such aged pipelines, trenchless methods are preferred to minimize the impact on transportation. The cured-in-place-pipe (CIPP) rehabilitation could be one of the most popular trenchless methods suitable for the cases with angular alignment and changing cross-section. However, according to the existing standards, no details are available on the performance of the rehabilitated parts of the damaged pipeline, including the effect of separated joint. This study designed and conducted laboratory testing on the composite pipe joint (the CIPP rehabilitated RCPs with a separated joint) with different scenarios, including radial and longitudinal loading tests. The radial test results indicated that, for a small separation distance, CIPP rehabilitation can restore the original function of a pipeline and improve its hoop strength. The longitudinal test revealed that the damage due to bending was controlled by the tensile strength of the liner material. The ultimate flexural strength decreased as the separation distance increased. However, pipelines may be subjected to additional loads due to flotation or subsidence, for which the longitudinal loading capacity is often the limiting parameter. For such conditions, it is necessary to confirm, by more research, whether the wall thickness is sufficient.