Road surface permanent deformations with a shallowly buried steel-reinforced high-density polyethylene pipe under cyclic loading

Steel-reinforced high-density polyethylene (SRHDPE) pipe is a new type of pipe used in roadways for drainage due to its obvious advantages, such as good corrosion resistance and light weight. In some projects, they are shallowly buried. To investigate the effects of the shallowly-buried pipe on the permanent deformation of road surface under cyclic traffic loading, two laboratory tests of an unpaved road with a buried SRHDPE pipe under cyclic loading were conducted. A 610 mm diameter SRHDPE pipe was buried in a compacted sand trench covered by aggregate or sand base courses in Tests 1 and 2, respectively. A Mechanistic-Empirical (M-E) model was calibrated with the laboratory test data and then adopted to conduct a parametric study on the road surface rutting. It was found that the SRHDPE pipe has very small deflection under the cyclic traffic loadings. The M-E model could predict the permanent road surface deformations well under cyclic loading before the road failed. Parametric studies showed that the road surface permanent deformation was intensified as the stiffness of buried pipe increased. The road surface deformation decreased as the pipe embedment depth increased and an optimum pipe buried depth existed to get the same road surface deformation between the road sections with and without a drainage pipe.