Structural behaviour of closely packed inverted egg-shaped sewer linings during installation and under various restraint conditions

The paper describes the results of a numerical parametric study aimed at studying the structural response of closely packed inverted egg-shaped sewer linings. The effect of various restraint conditions which simulate different temporary support systems that may be used by the contractors during the installation of the lining, and of different loading configurations which may arise at different stages of grouting the annulus gap between the lining and the sewer, have been thoroughly investigated. Covering the feasible range of geometric, material and loading parameters, comprehensive design curves, based on the allowable stress- and deflection-limit criteria, are presented. A comparison between the various types of restraints leads to enhancement factors for the permissible grouting pressure or, alternatively, to reduction factors in terms of the lining thickness that could be used in designing lining systems. Finally, the structural response of inverted egg-shaped sewer linings is compared with their egg-shaped counterparts.