Buckling of buried flexible culverts is defined as the loss of resistance to flexural deformations. Alternative theories are described. Then the procedures used by the most common current design codes are summarised and their limitations explained. The continuum theory is proposed as the best available approach to evaluate the buckling strength of buried flexible culverts because it most realistically models the soil properties and geometry. The suggested means of applying the continuum theory is presented. Example calculations show how the continuum theory results compare with those of existing codes. A major conclusion is that the substantial reduction in stability as structure size increases, as indicated by most approaches, is not correct according to the continuum theory. Commonly used theories are shown to be very conservative in most cases compared with the continuum theory. However, in some cases, for example shallow burial, the reverse may be true.
Abstract