Inelastic stability of liners of cylindrical conduits with local imperfection under external pressure

Liners are typically used to prevent leakage from large-diameter conduits (e.g., sewage pipelines, shafts, tunnels, or penstocks) to their surroundings. The liner is usually designed to resist buckling from external grout pressure during installation or from the external water pressure or internal negative pressure when the conduit is dewatered quickly for inspection and/or maintenance. This study uses the finite element method to investigate the inelastic stability of cylindrical liners with localized wavy imperfections. The liner's material is assumed to follow elastic-perfectly-plastic stress-strain relationship. The effects of the different geometrical parameters of the liner on its stability are studied. This is in addition to the effect of the liner's material properties (Young's modulus, Poisson's ratio, and yield stress) on its buckling pressure. Results of the study are expected to contribute to the understanding of the mechanical behavior of locally imperfect cylindrical liners when subjected to external uniform pressure, and also in the improvement of the associated design standards.