Apparatus for measuring pipe-soil interaction behavior using shallow 'Pipe-like' penetrometers

Reliable characterization of surficial marine sediments is essential to ensure the safe and economical design of subsea infrastructure for offshore energy facilities (e.g., seabed cables, pipelines, and shallow foundations). Conventional in-situ testing methods (e.g., cone penetrometer test or T-bar) require careful interpretation to account for the effects of shallow embedment, whereas laboratory tests are affected by sampling-induced disturbances, the impact of which can be significant at the low stress levels relevant to the design of subsea infrastructure. This article describes two novel box-core-sized shallow penetrometers - the hemiball and toroid - which mimic the shape of subsea pipelines and have been designed to reliably measure the strength, consolidation, and frictional properties of surficial offshore sediments. The development and specification of the actuator used to operate these probes is also described. Another major benefit of these penetrometers, which are intended to be used offshore for on-deck testing aboard a survey vessel, is their capability to generate effective stress interpretations of the soil behavior, and this is made possible because pore pressure transducers are installed and monitored throughout testing. The results of a first laboratory proof test are presented to illustrate the potential of this novel sensor concept.