2021 Volume 77 Issue 3 Pages 108-118
The aim of this study is assessing behaviors of buried flexible pipes at applying the internal loading method (ILM) for evaluating the strength of these pipes. In this study, behaviors of buried and un-buried pipes were compared using a polyvinyl chloride (PVC) pipe and a fiberglass reinforced plastic mortal (FRPM) pipe. As a result, the relationships between load and deformation of buried pipes showed nonlinearity, in which deformation ratio increases with the increment of applied load. The curve lines were thought to be classified into two stages; before and after the occurrence of the small shear failure in back-filling soil. Because of the restraint by the backfilling soil, the inclination of load-deformation curves of buried pipes became larger for both kinds of pipes. The difference of inclination between buried and unburied pipes was larger with the PVC pipe whose ring stiffness is smaller than the FRPM pipe. In the circumferential direction on the outside of buried pipes, tensile strains accrued especially at both of top and bottom parts of it. On the contrary, compressive strains gradually increased at the four portions oblique to the loading axis. This result indicates that expansion of the diameters in oblique direction is restrained by backfilling soil around buried pipes.
