Buckling strength of polymer liners used in sewer rehabilitation

Polymer liners are being used with increasing frequency for rehabilitation of damaged pipelines as part of infrastructure renewal in North America and elsewhere. An important consideration for these liners is the buckling resistance to fluid pressures acting on the outside of the liner (between the liner and the original pipe structure). Previous work has used unconservative solutions based on a different thermal buckling phenomenon or fluid buckling solutions for very thin liners. Nonlinear finite-element analysis is used to assess the stability of typical polymer liners fitted within a cracked rigid pipe. Slip and separation at the liner-pipe interface, the external fluid pressures, and the imperfect geometry of the damaged pipe are considered in the study of critical pressures. The liner buckling mechanism is reviewed, with emphasis on the impact of both the hoop and flexural stiffnesses. A parametric study is reported, to demonstrate the influence of thickness-to-radius ratio and imperfection size. Recommendations as to stability enhancement resulting from host pipe support are made. These could be used to design liners after examination of the theoretical results in relation to laboratory and field test data.