Study of fundamental behaviour of extremely low strength Clay

Abstract

Soil characterization of the upper 2 meters of the seabed is essential to optimize the design of hydrocarbon fields (mooring systems), wellheads, subsea completions, pipelines, anchors and mudmat foundations (Randolph, 2016). Additionally, it has an increasing importance for geohazard evaluation, particularly in submarine slides. In oceanic developments, where the water depth range from 200 to 3,000 meters, the geotechnical site characterization of the surficial sediments is particularly challenging, as generally extremely low to low strength, normally consolidated fine-grained deposits are encountered. Currently, different in-situ tests and sampling techniques are implemented to determine soil properties at large water depths; however, more accurate measurements are needed to improve the geotechnical designs and reduce project costs.
The preferred in situ tests when testing on extremely low strength clays are the full flow penetrometers, hence, this thesis investigates the fundamental behaviour of a full flow penetrometer by performing monotonic, cyclic and variable penetration rate tests on extremely low strength clays. The methodology followed included the design and construction of the test set-up, the determination of the system compliance, the execution of the penetration tests, the analysis and interpretation of the acquired data and the validation by comparing the results with laboratory vane shear tests.