Influences on Pipeline Interface Friction Measured in Direct Shear Tests

Abstract

This paper presents the design and use of an interface direct shear testing device called the Cam-shear apparatus. This device permits the testing of very soft marine clays against pipeline interface material, and can be utilised to determine the interface friction value and the soil strength. The results from a series of interface and soil–soil tests using reconstituted, reconsolidated marine clays are presented. The Cam-shear device is shown to be a useful tool for pipeline design, particularly where very low normal stress levels are required, with stresses ranging from 1 to 4.5 kPa presented herein. The results demonstrate that the peak interface friction value is influenced by the preconsolidation pressure (overconsolidation ratio), the rate of shearing (governed by the drainage condition) and the interface roughness (rough or smooth). The rate at which peak strength reduces is strongly dependent on both the rate of shearing and the interface roughness.