CONCENTRATION PROFILE WITHIN NONUNIFORM MUDCAKES

The concentration profiles within filtercakes of bentonite particles have been studied. A theoretical analysis of filtration is presented, and is compared to results obtained by cake dissection experiments. The constitutive relations which control short-term compaction of the cake are determined. Long-term cake-creep is also observed, and it is shown that the very simplest visoelastic models of cake compaction exhibit some, but not all, features of the observed behaviour. When the experimental results are combined with known values for the yield stress within the cake, the analysis predicts the hydraulic resistance of cakes which have been eroded by cross-flow: this is used to explain the apparent absence of erosion when cakes are subjected to laminar crossflow.