Electrokinetic strengthening of soft clay using the anode depolarization method

Electrokinetic stabilization is an innovative and cost effective ground improvement method for soft soils. With this method, stabilizing agents are electrically injected into the soils to achieve stabilization by means of ion exchange, precipitation or mineralization. The method is not yet widely accepted for common application as it improves the strength of soils only within a limited area. When coupled with a depolarization technique, the quality of the soil improvement is enhanced. Calcium ions are electrically injected into soils to replace monovalent ions while hydrogen ions, generated from electrolysis at the anode, are prevented from migrating into soils by continuous depolarization at the anode reservoir. However, hydroxide ions, generated at the cathode, are able to migrate into the soils. The injected calcium ions and hydroxide ions react with the dissolved silicates and aluminates in the clay to form cementing agents—calcium silicates and/or aluminum hydrates. Increases in strength of up to 170% immediately after treatment and up to 570% after a 7-day curing were measured. These results demonstrate that this simple technique could significantly improve the quality of electrokinetic stabilization in soft soils.