Model tests on soil restraint to pipelines buried in sand

Buckling of submarine pipelines may occur due to the action of axial soil frictional force caused by relative movement of soil and pipelines, which is induced by the thermal and internal pressure. The buckling may take place either laterally or vertically. The likelihood of occurrence of the buckling phenomenon is largely determined by the capability of the soil to resist pipeline movements. A series of large-scale model tests are carried out to facilitate the establishment of substantial data base for a variety of burial pipeline topologies. Fine sand is chosen as the supporting medium in view of Bohai Sea geotechnical conditions. Dry testing is employed for convenience. The pipes with diameters of 30 mm, 50 mm and 80 mm are used respectively. The pipes are buried in different depth-to-diameter ratios between 1 and 9. The uplift, lateral and axial resistances are recorded during the tests. Results show that the soil resistance depends on the pipe diameters and cover depth. For the same cover depth, the lateral soil resistance is more than twice as the uplift one. Based on the observed data, empirical formulas are established.