Volume 21, Issue 3 (September 1998)
Evaluation of Surface-Related Phenomena Using Sedimentation Tests
Sedimentation tests are suggested to assess the sensitivity of clay-water systems to environmental changes. A simple framework based on a parallel structure assumption was developed to analyze data from sedimentation tests. The slope of the relationship between the final sediment volume and the ionic concentration, plotted on a log-log scale, is related to the specific surface Sa, the double layer thickness ϑ, and to the specific gravity Gs. A new parameter, λ, the reactivity coefficient, where λ = Sa · ϑ · Gs · ρw, is introduced to help identification of reactive clay-water systems. High values of λ identify systems that are sensitive to changes in pore fluid characteristics. An experimental procedure is suggested to acquire relevant sedimentation parameters. Data collected during sedimentation tests of kaolinite, bentonite, and disaggregated Pierre shale, Mancos shale, and Queenston shale are used to verify the model. Agreement between experimental data and the model suggests that this simple technique can be used to identify reactive shales in the field. Other applications arise in tailing pond modeling, drilling mud management, and clay liner reliability assessment.