Slip Resistance Behavior of Coal Tar–Coated Steel Pipelines Buried in Clayey and Sandy Backfills from Ground Movement

AbstractSlip resistance of soil on buried pipelines develops from movement caused by faults, subsidence, and landslides. In areas with underground mining where subsidence is projected at the ground surface, pipelines crossing the subsided area will be subject to compressive and tensile stresses due to horizontal displacements in addition to vertical displacements. The soil–pipe interaction as well as slip resistance developed at the interface depends on surface roughness, backfill conditions, pipe displacement rate, and pipe depth. In this study, a total of six pipe jacking tests were performed on coal tar–coated pipes buried at depths of 1.2–1.8 m surrounded by clayey to sandy backfill materials. The test pipes were installed using typical pipeline construction practices and were exposed to expected rates of movement from longwall mining. Overall, the results from these field tests showed that for the same pipe depth, the slip resistance in clayey backfill sites was higher than at the sandy backfill site. The slip resistance of pipes under various displacement rates was measured and compared with empirical design guides. The analyses were also compared with results of pullout tests on buried pipes under similar conditions.