An analytical method is described for evaluating the bending moments in a poorly bedded section of pipeline buried beneath a highway when subjected to traffic loading. The method is mainly applicable to small diameter pipelines which are buried at shallow depth beneath a relatively weak pavement structure. The application of the analysis to a range of practical situations has been investigated. It is shown that soil deformation close to an undermined region of pipeline can effectively increase the extent of undermining and hence the bending moments induced by surface loading. Increased bending moments are also induced in a pipeline if the depth of cover is reduced, although the effect is not as great as might be inferred by considering only the maximum soil stress generated at pipe depth. Bending moments in the pipeline are also increased if the subgrade is made weaker. The mathematical model used for the analysis has been validated by comparing predicted bending strains, derived from the calculated bending moments, with the measured strains induced in a poorly bedded section of experimental pipeline by traffic loading.(A)

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