Abstract: In-service hydrocarbons must be transported at high temperature and pressure to ease the flow and prevent solidification of the wax fraction. The buckling of submarine pipelines occurs due to the introduction of axial compressive forces caused by the constrained expansions set up by thermal and internal pressure actions. Vertical buckling is particularly of interest with respect to buried submarine pipelines. To lay pipeline in trench with a certain depth is an effective measure to avoid vertical thermal upheaval buckling. Therefore, it is very important that study of the maximum resistance which soil can provide as well as the soil resistance changing procedure with the pipeline buckling amplitude. Fine sand was chosen as the soil medium in view of Bohai Gulf conditions. A model test was carried out to establish the relationship between soil resistance and pipeline displacement in laboratory. The pipeline segments with different diameters and different covered depths were used in the test. The soil resistance and the pipe segments vertical displacement were both recorded in great details. Then the numerical analyzing methodology was applied to simulate the model test procedure. Test data and analyzing results show that when the pipeline doing vertical uplift movement, process of soil resistance exertion can be affected by the buried rate of pipeline, when the buried rate is small, soil resistance decreases until stable after reaching peak; while when buried rate is large, the soil resistance doesn’t significantly reduced after its peak. In the practice, the maximum soil resistance can be gained when the pipeline upward displacement reaches to approximate 0.1D.

Key words: buried marine pipeline, vertical upheaval buckling, model test, soil resistance, numerical simulation