Study on the impact of ovality defect on structural stability of CIPP liner of drainage pipeline

Abstract

Cured-in-Place Pipe (CIPP) is a trenchless pipeline rehabilitation technology commonly used for repairing underground municipal pipes. It effectively, safely, and environmentally friendly resolves drainage pipe leakage and dripping issues by curing a new resin-impregnated liner inside the original pipe. However, in practical applications, ovality defects may occur in CIPP liners due to insufficient inflation, deformation of the original pipe, joint misalignment, and other problems. These defects have the potential to reduce the structural bearing capacity of the liners. To investigate the buckling mechanism of oval liner structures under external water pressure, two sets of OD 600 mm CIPP liner buckling tests were conducted. The critical buckling stress state and buckling mode characteristics exhibited similarities across liners with different initial ovalities. With an increase in the ovality defect of the liners from 0% to 5%, the critical buckling pressure decreased by 10.62%, while the maximum radial deformation displacement decreased by 62%. Existing models have shown an inability to accurately predict the buckling pressure of oval liners with an initial annular gap. Consequently, this study proposes an improved analytical solution for calculating the critical buckling pressure of liners with ovality imperfections under the influence of an annular gap, which aligns well with the experimental data. The conclusions drawn from this study provide substantial data support for ensuring the accuracy and safety of CIPP liner rehabilitation design.