Organic Leachate Effects on Permeability of Compacted Kaolinite

Abstract

A study on the effects of four organic fluids on permeability of compacted kaolinite is presented. A flexible wall permeameter set up was designed and constructed. Permeation fluids were 0.1% and 100% nitrobenzene, acetone, phenol and benzene, each mixed with 0.01 N CaSO4 as reference solution. Full saturation permeabilities (kh) were obtained under continuous backpressure at hydraulic gradients (ih) of less than 100 and effective stress of 69 kN/m2. All tests with chemicals at low concentrations resulted in slight decrease of kh. With pure solutions, however, the value slightly increased with acetone and phenol and significantly decreased with benzene and nitrobenzene. These results together with fabric studies indicated that changes in kh with organic fluids can be explained by the variations in the surface forces of interaction on clay particles affecting the flow characteristics. In order to assess the effect of the testing scheme, acetone permeabilities were obtained in both rigid and flexible wall permeameters. Excessive increases in permeability were observed with the rigid wall permeameters. The possibility of the effective stresses in flexible wall permeameters veiling the permeability changes due to organic fluid permeation was investigated. The results indicate that the observed increases in permeability with rigid wall permeameters can only be explained by the side leakages due to shrinking of the compacted clay when permeated with organic solvents.