Skirted foundations have been used increasingly to provide uplift resistance and to carry structural loads in offshore structures. When soft clay soils are encountered in a site, the soil shear strength is one of the major concerns in the design of skirted foundations with respect to the bearing capacity. Originated from the problem facing offshore engineering practice, this study is focused on electrokinetic strengthening of soft marine clays adjacent to skirted foundations. A series of laboratory electrokinetic experiments was conducted in a natural marine clay. A steel plate was embedded in the soil during the electrokinetic treatment to simulate part of a skirted foundation. The design, execution and results of the electrokinetic tests are reported. The results show that the undrained shear strength of the soil around the embedded steel plate was increased considerably after the electrokinetic treatment. It is also evidenced that the soil shear strength was further increased with time after the electric field was withdrawn, attributable to electrokinetics induced soil particle cementation during post-treatment ionic diffusion. In order to obtain uniform strength increase between the electrodes, to reduce energy consumption and to prolong the service life of electrodes, the effects of polarity reversal and current intermittence under a constant applied voltage were also investigated.
Skirted foundations have now become competitive alternatives to other more traditional foundation solutions such as piles and drag anchors for many types of offshore structures. They have been used increasingly worldwide as an attractive and, effective foundation solution in various types of soils, ranging from soft clays (Colliat et al., 1996) to dense sands (Tjelta, 1995). Skirted foundations have been used for floaters, tension leg platforms, gravity platform jackets, jackup rings, subsea systems and other protection structures (Anderson and Jostad, 1999).
