The simulation of additional soil overburden pressure through the use of a surcharge system is a technique commonly adopted in laboratory testing of pipe–soil interaction. This paper examines the influence of surcharge boundary conditions and pressure level on the axial sliding behaviour of a trenched pipeline surrounded by sand backfill. A novel testing tank is employed in conjunction with a pressure bag system to simulate overburden pressure; both flexible and rigid surcharge boundary conditions are considered. Cyclic axial displacements are applied to a heavy pipe buried in a narrow trench, using two different sand backfills. The test pipe is instrumented to measure (a) the axial soil resistance developed on an isolated central section of pipe (thus avoiding tank boundary effects), and (b) the normal and shear contact stresses at a number of points around the pipe circumference. The results show that the type of surcharge boundary condition (flexible or rigid) has a significant influence on laboratory measurements of both the axial resistance and circumferential pressure distribution of a buried pipe section. Application and subsequent reduction of surcharge pressure is also shown to produce ‘locked in’ normal stresses on the pipe, thereby increasing the axial resistance. The results show that careful treatment of the surcharge boundary conditions and the surcharge pressure history are required to avoid inaccurate predictions of field behaviour.

中文翻译：

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实验室研究轴向管-土相互作用时的覆盖压力模拟

通过使用附加系统来模拟额外的土壤上覆压力是在管道与土壤相互作用的实验室测试中通常采用的一种技术。本文研究了附加边界条件和压力水平对被回填砂包围的沟渠管道的轴向滑动行为的影响。一种新颖的测试箱与压力袋系统结合使用，以模拟上覆压力；柔性和刚性附加边界条件都被考虑了。循环轴向位移通过两个不同的回砂作用应用于埋在狭窄沟槽中的重型管道。试管的仪器用于测量（a）在管的隔离中心部分上产生的轴向土壤阻力（从而避免储罐边界效应），和（b）在管道圆周周围许多点的法向和剪切接触应力。结果表明，附加边界条件的类型（柔性或刚性）对实验室测量埋管段的轴向阻力和周向压力分布都具有重大影响。还显示出施加附加压力并随后降低附加压力会在管道上产生“锁定”法向应力，从而增加轴向阻力。结果表明，需要对附加费边界条件和附加费压力历史进行仔细处理，以免对野外行为做出不准确的预测。