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

中文翻译：

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不同粗度海相沙土的聚丙烯管界面强度

通过直接和表面覆盖土壤的界面剪切箱试验研究了聚丙烯管道涂料和海洋砂土的界面剪切强度。通过从现有的制造的钢管中取出聚丙烯样品，并制造出与北海海洋沉积物的典型组成和粒径分布非常相似的测试土壤。测试砂根据其粗颗粒分数而变化，0、15和35％的砂子保留在0·4 mm的筛子上。在松散状态和致密状态下，在与管道界面相关的极低应力（2·5和37·5 kPa）之间进行测试。实验结果表明，界面剪切强度与应力水平和相对密度有关，而粗颗粒部分起着适度的作用。表面特征和缺乏体积变形表明，剪切运动学主要是晶粒滑动而不是滚动。尽管由于表面试样的变化而有些分散，但界面效率在很大程度上是恒定的。由于固有的制造伪像，在某些聚丙烯表面上明显的接缝对界面强度的影响可忽略不计。评估，讨论了界面强度，归一化粗糙度和肖氏D硬度之间的关系，并将其与其他工作的结果进行了比较。由于固有的制造伪像，在某些聚丙烯表面上明显的接缝对界面强度的影响可忽略不计。评估，讨论了界面强度，归一化粗糙度和肖氏D硬度之间的关系，并将其与其他工作的结果进行了比较。由于固有的制造伪像，在某些聚丙烯表面上明显的接缝对界面强度的影响可忽略不计。评估，讨论了界面强度，归一化粗糙度和肖氏D硬度之间的关系，并将其与其他工作的结果进行了比较。