砂土对埋设管线约束作用的模型试验研究

Model tests on soil restraint to pipelines buried in sand

屈曲剧变是海底管线失稳破坏的重要形式之一。运营中的高温、高压是导致海底管线发生屈曲剧变的直接条件,而地基土体对管线的约束作用是导致管线屈曲的根本原因。研究表明地基土对管线作用力的大小决定着管线发生屈曲变形的形态。采用取自渤海湾的细砂进行了室内管土相互作用试验,研究不同直径、不同埋深的管线竖直向上运动、水平向运动以及轴向运动时土体抗力的发挥过程。试验结果表明土抗力的发挥过程与管线的埋置率有关;埋深相同的管线水平向运动时受到的抗力比竖直向运动时大2倍以上;结合试验结果提出了适于计算渤海湾砂土地基对埋设管线约束力的经验公式。

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.