Buckling of Thin-Walled High Density Polyethylene Liners Encased in Rigid Pipes under External Pressure and Thermal Effects

The thin-walled close-fitting high-density polyethylene (HDP) liners are usually used to rehabilitate the damaged sewer pipes in the trenchless technology. The liner is installed on the inner surface of the pipe, resulting in a small curing shrinkage gap (separation) between the liner and pipe. When the pipe-liner system is surrounded by saturated soil under groundwater level, the water flows into the permeable pipe and yield hydrostatic pressure at the outer surface of the liner. In addition, a temperature variational field may generate on the pipe-liner system when it transmits the hot crude oil. An upward thermal displacement may occur on the crown position of the liner due to the expansion of the liner material. Furthermore, the hoop compressive stresses generate on the liner wall due to the confinement of the outer pipe. This paper focuses on analyzing the buckling behavior of the thin- walled HDP liners under external pressure and variational thermal field simultaneously. The closed-form analytical expressions are developed to determine the critical buckling pressure. This analytical solution is verified successfully by developing a finite element model (FEM). The numerical buckling pressure for the confined liner agrees well with closed-form expressions. The thermal field shows a substantial effect on the buckling pressure. Finally, the effects of temperature field and the gap on the buckling pressure are discussed.