A SEMIANALYTICAL ANALYSIS OF COMPRESSIBLE ELECTROPHORETIC CAKE FORMATION

Leaks in geomembrane liners of waste landfills and liquid impoundments cause chemical contaminants to leak into the subsurface environment. A mathematical model is presented to simulate electrophoretic sealing of impoundment leaks. The model describes the formation of a compressi ble clay cake because of electrical and gravitational forces. The mode l includes mass balance equations for the solid-particles and liquid p hase, modified Darcy's law in an electrical field, and Terzaghi's defi nition of effective stress. The formulation is presented in the Euleri an coordinates. The resulting second-order, nonlinear partial differen tial equation and the lower boundary condition are linearized to obtai n an analytical solution for time-dependent settlement. After discreti zing in time the analytical solution is applied to simulate compressio n of an accreting Sediment. In the; simulation of an accreting sedimen t, solid fluxes on either side of suspension/sediment interface are co upled using a no-jump condition. The velocity of a discrete particle i n the suspension zone is assumed to be equal to the algebraic sum of e lectrophoretic and Stoke's settling velocities. An empirical relations hip available in the literature is used to account for the effect of c oncentration on the velocity of solid particles in the suspension zone . The validity of the semianalytical approach is partially verified us ing an exact steady state solution for self-weight consolidation. The simulation results obtained for a set of material parameters are prese nted graphically. It is noted that the electrokinetic consolidation of sediment continues even after the completion of electrophoretic settl ing of all clay particles. An analysis reveals that the electrophoreti c cake formation process is quite sensitive to voltage gradient and th e coefficient of compressibility.