A large scale experimental study was conducted on electrokinetic cementation of calcareous sand for offshore foundations. A steel tube, 200 mm in diameter and 400 mm in length was used as a model caisson. Calcareous sand and seawater from the coastline of Western Australia were used in the study. The cementation treatment consisted of two phases: the treatment after caisson installation (phase "A") and the remediation treatment after pullout failure (phase "B"). Twelve electrodes made of perforated steel pipes were installed around the caisson. A dc voltage of 6 volts with current intermittence and polarity reversal was applied with the caisson serving as one electrode and six of the twelve electrodes serving as the second electrode in phase "A" of the treatment and the other six electrodes and the caisson in phase "B" of the treatment. A control test with identical configurations was also set to provide baseline data. The results showed that the pullout resistance of the foundation model increased by 119% in phase "A" and by 214% in phase "B" of the treatment as compared with the control.
Calcareous sediments with more than 30% calcium carbonate cover approximately 34 % of the Earth's surface (Sverdrup et al., 1942). Many oil reserves, such as those in Saudi Arabia, India, Australia and the Caribbean are located under calcareous soils (Murff, 1987; King and Lodge, 1988). Calcareous soils in general are highly compressible and prone to crushing compared to siliceous particles at similar stress levels. Exploration of oil and gas fields in offshore sites around the world and expansion of recent projects of wind farms has resulted in the construction of many oil platforms and farm towers on calcareous soils of grain sizes ranging from sand to clay.
