Experiment and evaluation model of liner design for renewal of deteriorated reinforced concrete pipes utilizing cured-in-place-pipe technology

Cured-In-Place-Pipe (CIPP) is an emerging trenchless rehabilitation technology for repairing urban drainage pipes growing significantly in China. However, overestimated external loads due to a completely deteriorated-pipe assumption may increase conservatism in the CIPP liner structure design. In this study, ring stiffness test machine was employed to quantify the bearing characteristics of pipe-liner system. The concrete and reinforced concrete pipes with an inner diameter of 200 mm, which deteriorated to several states, were renewed with CIPP. Digital Image Correlation (DIC) was employed to reveal the contact characteristics between the host pipe and CIPP liner under external loads and the mechanism of loads transferred from the pipe to the liner. An evaluation model for load-bearing performance of reinforced pipe was established. Parametric studies were carried out including lateral load distribution angle, concentrated load dispersed angle, and lateral interactions. Furthermore, a case study was conducted in conjunction with the indirect design method for buried pipes, and then the improved model was compared with experiment results. An average value of 20 % reduction in CIPP liner thickness was achieved by employing the modified model than the ASTM standard. This study can serve as a database for engineers designing CIPP rehabilitation projects for concrete pipes whose structure has not been completely damaged.