Soil restraint against oblique motion of pipelines in sand

The soil restraint on pipelines due to oblique relative movement betwen the pipeline and dry loose sand was investigated. Model pipes 1.22 m long with diameters of 38.1, 76.2, 152.4, and 228.6 mm are obliquely moved from vertical to horizontal direction in the drag box to study the soil restraint of the oblique pipes with various relative velocities. All test results indicate that the dimensionless ultimate soil restraints have a power law relationship with the pipe velocity. The velocity exponent increases slightly with the oblique angle and embedded depth of the pipe. Furthermore, the soil restraint also increases with both the pipes oblique angle and embedded depth. Most of the increase in the soil restraint is associated with the oblique angles in the interval between 45 and 90°. The limit equilibrium model succesfully predicted the soil restraint of the pipe. Normailized force–displacement relationships of soil–pipe interaction could be represented by two-constant hyperbolic equation. The findings show that the first constant value, a, increases, whereas the second value, b, decreases with the oblique angle, respectively. Key words: pipelines, soil restraint, oblique motion, sand.