Numerical analysis of the mechanical behavior of separated joints in underground pipelines rehabilitated by cured-in-place pipes

Abstract

For the old underground pipelines in Taiwan area, damage to the pipe joints due to factors such as overloading, poor backfilling, and liquefaction is a continual concern. Damage to joints includes fracture and separation, and the consequences of such damage include leaking and subsidence. For the rehabilitation of this type of damaged pipeline, trenchless methods are optimal because of their minimal impact on transportation. Cured-in-place pipe (CIPP) is a popular trenchless rehabilitation method suitable for the cases with variable pipe alignment and cross-sections. However, according to the American Society for Testing and Materials F1216 standards, CIPP rehabilitation is designed for cases where a completely damaged pipeline is to be replaced by a new one, and the guidelines do not provide details on the rehabilitation performance of the damaged parts, which was the focus of this study. In this study, the performance of separated joints after CIPP rehabilitation was numerically analyzed. The numerical model was calibrated by using the laboratory test results, before applied to simulate the rehabilitated pipelines with various geometries and loading conditions. The influence of control factors (e.g., backfill, and interface) on CIPP rehabilitation performance was then analyzed in detail. In order to further understand the effect of different resin materials used for CIPP, this study also conducted experiments and numerical analysis on resins commonly used, including epoxy resin (EP), vinyl ester (VE) and unsaturated polyester (UP). The results of this study can be applied in engineering design optimization as well as industry guideline development.