Parametric study for buckling of liners: effect of liner geometry and imperfections

Non-linear Finite Element analysis is used to investigate liner stability under external fluid pressure. Liners are assumed to be circular or elliptical with initial local or global geometrical imperfections. The typical local imperfections examined are defined as a wavy intrusion into the liner. Global imperfections are also investigated in the form of an ovality in the liner or a gap between the liner and the host pipe. A parametric study is undertaken to determine the effect of the initial liner geometry. It is shown that critical external fluid pressure depends heavily on the ratio of liner thickness to radius. Local geometrical imperfections and the size of the gap between the liner and the host pipe have very substantial effects on the liner buckling strength particularly for thin liners. The results of the parametric study are used to develop a new design method for liners used in rigid pipe rehabilitation.