Offshore Cone Penetration Test and Its Application in Full Water-Depth Geological Surveys

Abstract

Characterizing seabed sediments is one of the most important processes in marine engineering surveys. Marine sediments, which are characterized by low strength, typically consist of soft fine-grained sediments (either clay, or in some regions, carbonate muds and silts) that have been deposited relatively slowly. Sampling these soft sediments is extremely difficult, and in situ testing is preferable. Cone penetration test (CPT) is widely used due to its prominent advantages in accurately determining the physical-mechanical properties and types of seabed sediments. Due to the world’s escalating demand for energy, combined with the continued depletion of oil and gas reserves in shallow waters, offshore engineering has moved beyond the immediate continental shelf into deeper waters and untested environments, thus posing a challenge to the operating water depth of CPT. The paper presents an overview of recent developments and applications in CPT technology associated with different water depths, including the cone penetration equipment suitable for the beach/shallow sea, the areas with normal water depth, and the extremely deep sea. Furthermore, the nature of CPT design has changed radically partly due to the types of engineering and partly because of the specific nature of the seabed sediments. Thus, the CPTs with multiple functions are also reviewed.

Model prediction controller for penetration mechanism of seabed cone penetration test system

“…where, is the error quantity, , and is predicted by the model, . Define the new state quantity: (6) Substitute (6) into Equation (5) to get the expression for the new state space: (7) where ( 8) is shortened to , is shortened to .…”