Buckling Behavior of Loosely Fitted Formed-In-Place Pipe Liner in Circular Host Pipe under External Pressure

The formed-in-place pipe (FIPP) is a trenchless technology used for pipeline rehabilitation. It folded PVC that expands through thermoforming to fit tightly inside the host pipe. However, deficiencies during construction of FIPP liners such as insufficient inflation, misalignment and initial deformation will lead elliptical liner, which affects load-bearing performance liner makes it susceptible buckling failure. In this paper, behavior loosely fitted under uniform external pressure was investigated by resistance test finite element model. pre- post-buckling equilibrium paths verified results indicated value dimension ratio significantly reduce critical pressure. With increasing major axis pipe, reduction effect on caused increase in ovality diminish. Different values changed range detached portion, affected parametric studies modified design model from ASTM F1216, established predict reduced average difference rate 23.43% 5.52%.