Structural Design of Close-Fit Liners in Fractured Rigid Circular or Non-Circular Gravity Pipes

Abstract

The French standard for the design of liners for gravity pipe application offers a fully analytical approach for the design of circular and noncircular liners under groundwater pressure. Liners’ geometrical imperfections, which dramatically decrease the resistance of the lining to groundwater pressure, are treated using single or combined analytical correction factors that apply to quantities (buckling pressure, deflection, hoop force, and bending moment) calculated based on the perfect profile. This paper presents analytical calculations that establish correction factors for close-fit liners encased in fractured rigid circular and noncircular host pipes. An approximate solution is generated by assuming an allowable displacement function and minimizing the potential energy. It is shown that the effect of fractures on liners’ resistance to buckling is governed by the rotation angle of the hinge formed by the fracture, which imposes an angular step to the liner. Finite-element simulations of liners encased in fractured rigid circular, elliptical, and egg-shaped pipes are presented, and showed good agreement with the analytical solution.