Easing extraction of spudcan foundations through electrokinetic phenomenon

Extraction of mobile jack-up rigs’ spudcan foundations in soft clay sediments is a time-consuming process. Suction at the base of an installed spudcan dictates the extraction resistance. Consequently, any reduction of the base suction will ease the extraction process and reduce offshore time and hence cost. This paper experimented the potential of using electrokinetic phenomena such as electrode reaction and electroosmosis for reducing the base suction. Two series of experiments were carried out. First series concentrated at observing hydroxyl (OH⁻) generation from a half-spudcan to assess the effectiveness of the new method of applying electric current in kaolin clay. Second series focused on observing gas generation around an installed full-spudcan and crack formation through the kaolin and Tokyo Bay clay deposits to evaluate the potential of reducing base suction. The results of the experiment showed that the new method is effective for applying current to the entire embedded spudcan, where the anode is set in the solution above the ground and the spudcan serves as the cathode. The results of X-ray micro tomography imaging indicated that gas and crack generated around the spudcan and shaft that could potentially reduce the base suction.