The effect of a berm on the lateral resistance of a shallow pipeline buried in sand

Abstract

As the development of offshore oil and gas exploration moves into deeper waters, pipelines experience lateral buckling due to high temperatures and high pressures in submarine. The pipe–soil interaction plays a critical role in the thermal buckling characteristics of pipeline. Large-amplitude lateral movements of pipelines tend to cause soil accumulation in front of pipelines. The accumulated soil in front of pipelines is generally called as “berm”. The berm is an important factor in forecasting the changes in the lateral buckling characteristics of pipelines. In this study, a pipe segment with 16-cm outer diameter is considered as the object. Pipe–soil interaction model tests of lateral movement under different initial embedments and different pipe segment weights of 0.05, 0.1 and 0.15kN/m are performed in sand. The large deformation behaviour of seabed and the changing process of berms are investigated; a formula to calculate the berm resistance is also proposed. Compared with the existing calculation methods, the lateral residual resistance including the influence of berms is more significant in this study if the weight of the pipe segment equals or exceeds 0.1kN/m. However, the existing calculation methods tend to exaggerate the lateral residual resistance when the pipe segment weight is less than 0.05kN/m.