The results of a series of experimental tests on pull out capacity of a typical horizontal plate anchor under different sequential vertical loadings are presented in this paper. The loading comprises of a load applied under undrained conditions followed by consolidation of the soil under sustained loading and then undrained loading up to the failure of the foundation system. This sequential loading simulates the loads applied to the anchors of floating platforms during calm weather and during an ocean storm. For comparison, another anchor was also loaded up to failure under undrained conditions. The anchor is idealized as a circular plate embedded in a normally consolidated soft clay. The results of the experimental studies show that dissipation of pore pressures generated in the soil around vertically loaded anchors not only does not adversely affect the capacity of the anchors, but also increases their peak capacity.
Both the exploration and exploitation of hydrocarbons are heading more towards deeper waters. Tension leg, taut and semi-taut leg and semi-submersible platforms are among the options that are increasingly used in deep waters. With the greater depths there are greater needs for more robust anchoring systems to transfer predominantly tensile forces to the ocean floor. Vertically loaded anchors, or simply plate anchors, are among the few technologies currently used for this purpose in deep waters. The last 20 years has seen a great increase in the capacity of drag embedment anchors, mostly due to improvements in design that have allowed a greater penetration in softer seabeds. This higher capacity has in turn allowed the extension of development into areas with much deeper water and more hostile environmental conditions. Vertically loaded anchors have the potential for reducing the cost of anchoring system although this requires more confidence and experience in the design of the anchors.