DEVELOPMENT OF PORE PRESSURES BY NONUNIFORM ELECTROOSMOSIS IN CLAYS

A theory is presented for the development of nonuniform pore pressures during electrokinetic treatment caused by local deviations in the ele ctric field intensity and soil surface chemistry. The electric field i ntensity and surface (zeta) potential are the driving parameters for e lectroosmosis in any local soil region; when these parameters vary wit h space, there is a nonuniform driving force that must be balanced by a decrease or increase in local pore pressure. The theory is derived f or the case of a rigid capillary, and is based on the assumptions of i ncompressible flow, negligible consolidation, the Helmholtz-Smoluchows ki equation, and constant hydraulic conductivity. Comparisons of the t heory with laboratory measurements made by Eykholt in 1992 are present ed for one-dimensional electroosmotic flow through saturated kaolinite plugs. Measurements of the net electroosmotic flow rate, pore pressur e and electrical potential profiles, and hydraulic conductivity, can b e used to assess, at least qualitatively, the relative contributions t o electroosmosis in soil regions along the profile. The k(eo) profile simulations provided here did not correlate well with measured chemica l profiles. Future success of the simulation strategy will likely depe nd on two factors: accurate electric field measurements and electrokin etic characterization of soil sections. (C) 1997 Elsevier Science B.V.