Keying Process And Ultimate Pullout Capacity Of The OMNI-Max^TM Anchor Shallowly Embedded In NC Clay

With the increasing demand for oil and gas energy, the exploitation of offshore oil and gas are gradually moving to deep water. Therefore, efficient anchoring systems for mooring drilling rigs and floating processing facilities to the sea bed are increasing and play a significant role in the whole system. The OMNI-MaxTM anchor is a newly developed dynamically penetrating anchor (DPA). Once inserted in clay by its self-weight and the kinetic energy from the free fall through the water column, the anchor was rotated/keyed under loading initially and then dove deeper as designed. Positioning in seabed soils is important for OMNI-MaxTM anchor because the working performance of the OMNI-MaxTM anchor is closely related to the embedment depth and orientation of the OMNI-MaxTM anchor and the properties of the surrounding soils. However, the keying behaviors of the OMNI-MaxTM anchor have never been clearly known, especially the trajectory of the anchor in soils. Hence, the motion trajectory and capacity are two main issues for the further application of the OMNI-MaxTM anchor in offshore engineering. The current study investigated the development of the OMNI-MaxTM’s movements, the ultimate embedment depth and the pullout capacity during keying in normally consolidate (NC) clay by employing a plasticity model of yield envelops. A thorough parametric sensitivity study in the padeye anchor pullout angle, gradient of soil strength, padeye offset angle, chain friction coefficient and chain-soil interaction properties were investigated. The results indicate that these parameters, especial the loading angle and the padeye offset angle, have significant effects both on the anchor trajectory and pullout capacity.