Buckling experiments on polyethylene liners with egg-shaped cross-sections

In Germany, egg-shaped concrete and masonry sewers can be renovated with short thermoplastic liners of corresponding cross-sections. The decisive variable for dimensioning of the wall thickness is the groundwater pressure on the liner surface. The necessary calculations are, as a rule, executed by data processing procedures. Buckling experiments are important for the development of the theoretical approaches. The specific material behaviour of thermoplastics, and in particular their creep tendency, is considered in the experimental planning. In total, the results of 11 buckling experiments with different imperfections (none, annular gap or local imperfection) concurred with the buckling pressures determined by calculation. Ten small-scale experiments and one full-scale test were carried out at constant external pressure as creep tests of over 2–3 h in duration. The evaluation of the 11 experiments shows that the application of the German design code ATV-M 127-2 for the calculation of the stability of egg-shaped profiles subjected to water pressure (host pipe states I and II) is suitable. The small-scale experiments showed that less extensive set-ups still supply useful information when examining the load-carrying capacity of non-circular liners. Such experiments could be carried out within the framework of first examinations and for quality assurance.