Soil Restraint to Oblique Movement of Buried Pipes in Dense Sand

The soil restraints to oblique movement of buried pipes in dense sand were investigated. Model pipes 0.61 m long with diameters of 152.4, 228.6, and 304.8 mm were obliquely moved from an axial-longitudinal to a lateral-transversal direction in a large scale drag box to study the associated longitudinal and transverse soil restraints on the pipes in the shallow buried depth. All the experimental results indicated that the longitudinal soil restraint to the axial movement of the pipes could be estimated as the product of the average of the vertical and horizontal earth pressures at the centerline of the pipe and the tangent value of the soil-pipe friction angle. For the lateral movement pipes, three different theoretical methods were used to analyze the transverse soil restraint. Among these, the modified Meyerhof approach with the assumption of a rupture surface of logarithmic spiral arc was closer to the experimental results compared to the planar sliding surface approach. For the oblique movement pipes, the longitudinal soil restraint decreases, whereas the transverse soil restraint increases with increasing oblique angle. Moreover, the longitudinal and transverse soil restraint of the oblique angle pipes could be obtained by multiplying the corresponding cosine and sine values of the oblique angle with the associated longitudinal soil restraint of the axial pipe and the transverse soil restraint of the lateral pipe, respectively. The findings also indicate that the scale effects are minor for sizes up to 304.8 mm of the pipe diameter tested herein.