Analytical solution of electroosmotic-surcharge preloading coupled consolidation for unsaturated soil via Electric Prefabricated Vertical Drains (EVDs)

Electric prefabricated vertical drain made of new geosynthetic materials has the advantages of corrosion resistance, good water filtration, and unobstructed drainage. It has been used in unsaturated soils for embankment and slope stabilization as well as roadbed improvement. A theoretical model of the axisymmetric, free-strain consolidation for unsaturated soil under the coupled electrical-flow-mechanical fields considering radialvertical flow is formulated, using the homogenization theory, method of separation of variables, and BesselFourier series orthogonality. The relevant cases of saturated and unsaturated conditions are compared with the current analytical solution to examine the validity. The spatial and temporal distributions of excess porewater and pore-air pressure are accurately reflected in the proposed solution, and its variation under electric fields is effectively displayed. The numerical calculations are also performed to investigate the effects of various important parameters, such as the single-layer unsaturated soil thickness, the effective voltage, and the radial water-to-electrical permeability ratio, on the excess pore-water pressure, excess pore-air pressure, and surface settlement. It is observed that the final negative pore-water pressure and the final settlement increase linearly as the effective voltage increases.