DRAINED INTERFACE STRENGTH BETWEEN PIPELINES AND CLAYS USING TILT TABLE AND DIRECT SHEAR TESTS

Abstract

The design of high-pressure high-temperature pipelines (HPHT pipelines) is mainly governed by pipe-soil interaction considerations. Over the past few years, a number of studies have set as their goal to reliably characterize the soil-pipeline interface behavior. Independent research groups utilized different test setups and methodologies to that effect, with the tilt table test and the interface direct shear test being the most common testing approaches. To date, there are no published efforts that show direct comparisons between results from these two testing systems. The objectives of this study are to (1) design and fabricate tilt table and interface direct shear testing setups that are capable of measuring the drained interface resistance between pipelines and clays, (2) use these setups to study the effects of low effective normal stresses and type of pipeline coating on the drained clay-pipe interface response, and (3) compare the results from tilt table and interface direct shear tests under identical interface and soil conditions. The results allow for drawing conclusions on the adequacy of the two testing methodologies in determining interface strength properties that will aid the design of offshore pipelines in soft clays.