Polypropylene pipe interface strength on marine sandy soils with varying coarse fraction

The interface shear strength of polypropylene pipeline coatings and marine sandy soils was investigated through direct surface-over-soil box testing. Polypropylene specimens were acquired by removal from existing manufactured steel pipes test fabricated to closely resemble typical compositions particle size distributions North Sea sediments. sands varied according their coarse fractions, with 0, 15 35% being retained on a 0·4 mm sieve. Testing carried out at the very low stresses pertinent interfaces, between 2·5 37·5 kPa, in both loose dense states. experimental results suggest dependency stress level relative density, fraction playing modest role. Surface characterisation lack volumetric deformation suggests that shearing kinematic is predominantly grain sliding rather than rolling. Interface efficiency largely constant despite some scatter due variability surface specimens. distinct seams apparent surfaces as inherent manufacturing artefacts had negligible influence strength. relationship strength, normalised roughness Shore D hardness assessed, discussed compared other works.