Centrifuge modelling utility pipe behaviour subject to vehicular loading

Centrifuge model tests of buried flexible pipes in dry sand subjected to surface traffic loads are presented. Model pipe tests were performed at 25 gravities (25g) of a prototype pipe 355 mm in diameter. Pipe behaviour was observed for different burial depths of 0.5, 0.75, 1.0 and 1.5 m; and load eccentricities of 1 and 2 pipe diameters. Results show that pipes buried at shallower depths are subjected to significantly greater bending moments and corresponding shear stresses. When the load is applied at an eccentricity, if the pipe remains within the zone of stress influence, a comparable magnitude of maximum moment is anticipated. An initial series of 20 cycles were also carried out. Results indicate an amount of ‘locked-in’ bending moment upon unload; a phenomenon more evident for the shallower buried pipe.