Influence of boundary conditions on transient excess pore pressure during electrokinetic applications in soils

Application of electric currents through saturated silt and clay-rich soils induces electrochemical effects that influence the mechanical and hydraulic behaviour of soft soils. The transient effects of electro- and geo-chemical changes on pore pressure evolution in soil are poorly understood. A major issue, the transient development of non-linear geo- and physico-chemical conditions between the electrodes, is evaluated in this study. An experimental investigation was conducted to provide an understanding of the mechanisms that affect pore pressure or suction development along the sample and consequent transient and non-linear changes. A natural silty soil was used because it accounts for the complex physical and chemical interactions that originate during treatment in the field. Tests were conducted with free drainage at the boundaries and under constant current intensity. The experimental investigation results highlighted the importance of the boundary chemical conditions on the development and transient changes in excess pore pressure along the sample. In particular, the generation of high potential gradients in the first few millimetres of the soil sample dominates the overall pore pressure distribution and behaviour. A relationship between the maximum pore pressure developed and the applied current density is evaluated.