There are numerous analytical and empirical statements for describing the bearing and failure behaviour of self-supporting liner with circular cross sections and these have been defined for very different border conditions and thus make their direct utilisation in practice difficult without knowledge of the theoretical backgrounds. As a rule, they only account for the failure of stability of circular, free, or externally coated pipe cross sections under evenly distributed external pressure loading and are to be used only with reference to their particular border conditions as a first estimate of the maximum acceptable loads. Thus, the buckling formula according to Glock for small wall thicknesses t/Dm
A description of the failure behaviour of the ovoid cross section is possible by means of FEM with acceptable effort. The deformation behaviour is characterised with reference to the gap width, wall thickness, material properties and added imperfections as well as by single waved, asymmetrical and two-wave symmetrical deformation figures. The mutual reciprocal effects between gap width, pre-deformation and wall thickness, as well as the material properties and the expansion of the contact region cannot be acquired by analytical statements and should be investigated by FEM analyses on a case-specific basis.