Soil-Pipe Interaction of Heated Oil Pipelines

A study is presented analyzing the distress frequently encountered in buried heated oil pipelines due to the expansion and contraction producing soil-pipe interface shear and cyclic movements. This movement can damage the coating of the pipe and result in corrosion failure. The magnitude of the cyclic shear stress and movement depends on temperatures, soil properties, and pipeline design items such as the length of casing, bend, and straight pipe sections. Two important factors are the coefficient of horizontal subgrade reaction and the soil-pipe interface shear parameter. The interface shear parameter is unique to the heated pipeline problem and can serve as a coating performance and selection criteria. Methods to calculate pipe movements and ways to restrain such movements are analyzed. Actual field measurements of a heated oil pipeline are compared with theoretical calculations.