Research On Pipeline Penetration And The Lateral Soil Resistance

With the rapid development of the world marine petroleum industry， submarinepipelines have been widely used in the offshore oil and gas exploitation. There aretwo significant connected issues in the submarine pipeline design: pipelinepenetration and the lateral soil resistance. In this paper， both theoretical calculationmethod and numerical simulation method are adopted for pipeline penetrationresearches. For the researches on the lateral soil resistance， model test is as thethird method to be adopted. The main research contents and results are as follows:The fine sand and soft clay which are distributed widely in the upper soil layer ofBohai Gulf were chosen as medium in the pipe-soil interaction laboratory tests. Thepipe segments lateral displacement and the corresponding suffered soil resistancewere measured during the tests. The whole process of pipeline penetration wassimulated by the application of CEL method. The simulation results were comparedwith the existed calculations and confirmed the applicability of FEM method. Theanalysis model of pipe-soil interaction was also established to simulate the process ofthe pipe lateral movement. Based on all of these above， the actual size pipelineswere adopted to simulate the lateral soil resistance.The researches show that: as to the Bohai soft clay， the Prandtl calculation isreasonable when the penetration depth is less than0.5D; the Muff calculation is morerational when the penetration depth is more than0.5D. The real penetration depthcould be determined to contrast with the CEL result. No matter in sand or soft clay，the relationship between the pipeline displacement and lateral soil resistance are thesame. Initially the lateral soil resistance increases rapidly with the pipelinedisplacement. As it reaches a certain value， it will never change with thedisplacement. At the same embedment depth， larger the pipe diameter is， higherthe peak soil resistance and the corresponding displacement are. In according to thetest and simulation results， a simplified calculation for the peak lateral soil resistanceand the corresponding displacement is proposed.