Electro-osmotic chemical treatment of clay with interbedded sand

Abstract

Electro-osmotic chemical treatment is a ground improvement method that injects chemical solutions into the soil during electro-osmosis to increase soil strength. However, previous studies have shown that the electro-osmotic chemical treatment method is inadequate when applied to clay with interbedded sand. The reason was that the injected chemical solutions may leak from the interbedded sand during electro-osmosis, resulting in poor improvement of the clay. In this study, a small-scale test cell (0·23 m wide, 0·44 m long, 0·32 m deep) with a pair of electrodes were designed to develop an appropriate electro-osmotic chemical treatment process for clay strata with sand layers. A clay stratum overlying a sand layer was used to make the conductivity of the sand layer relatively high. The results show that the permeability coefficient of the interbedded sand could be effectively reduced to 10−5–10−6 m/s by first injecting sodium silicate into the sand by pressure, followed by injecting calcium chloride by electro-osmosis. The calcium chloride could therefore effectively be flowed in the clay during electro-osmosis after decreasing the permeability coefficient of the interbedded sand, resulting in strength improvement of the clay. The strength of the clay was increased by up to 20 times the original strength near the cathode region.