THE HYDRAULIC PERMEABILITY OF BENTONITE SUSPENSIONS WITH GRANULAR INCLUSIONS

Compacted clays were made by filtering aqueous suspensions of bentonite. Some suspensions were weighted with barite, which formed granular inclusions in the filter cake. The desorptivity S and the void ratio e were obtained over a range of differential pressure P. The outflow ow inversion method was used, with the S(P) and e(P) data, to obtain the diffusivity D(e) and the permeability k(e) of the filter cakes derived from the suspensions. The D(e) data show a maximum. The permeability k(e) for both weighted and unweighted suspensions increases monotonically with e. For barite volume fractions (phi(b)) up to about 0.6 the filter cake permeability k(e) is shown to be largely determined by the permeability of the interstitial bentonite-water matrix. For phi(b) > 0.6, k(e) increases rapidly with increasing phi(b), and a simple analysis in which non-interacting barite particles perturb the permeability of the bentonite gel is inadequate. This is attributed to load-bearing structures of barite particles which prevent the compaction of the interstitial bentonite.