A pipe-segment testing device for axial pipe-soil shearing and comparison of interface shear behaviour at different scales

The predictions of axial walking and lateral buckling in pipeline design are highly dependent on the axial pipe-soil shear friction. Except the limited in-situ data from previous projects, the axial shear friction is often determined by interface direct shear tests with element-scale pipe and soil samples. However, this methodology cannot reflect the effects of pipe curvature and increasing embedment as axial shearing proceeds. It is also infeasible for soil beds with large granular sizes and irregular surface. This paper describes a novel pipe-segment testing device developed at the University of Bristol specifically for the on-bottom pipe-soil shear tests at a comparatively large scale. The axial shear tests are conducted with a polypropylene pipe on two test sands of different granular sizes and densities. The testing results are further compared with those of element interface shear tests to investigate the curvature and scale effects on the axial pipe-soil shear strength. The observations validate the feasibility and reliability of axial pipe-soil testing on the new test rig, which provides beneficial reference for pipeline design when scaling the laboratory test results up to in-situ conditions, with the aim of reducing the uncertainties on pipe-soil interaction.