Influence of test method on swelling pressure of compacted clay

Abstract

Swelling pressure of clays is an important parameter required for the design of a variety of structures founded on expansive soils. Out of many methods available to determine the swell pressure in the laboratory, odometer method is popular because of its simplicity. Three odometer methods are commonly used to determine swelling pressure, such as swell consolidation method (Method A), different pressure method (Method B) and constant volume method (Method C). Comparison of values obtained by the three methods shows that Method A gives highest value, Method B gives the lowest value and Method C give intermediate value. The possible reason for this difference is brought out in this paper. Experimental evidence, from permeability measurements and SEM, shows that fabric alteration from a flocculated state to dispersed state occur in Method A due to swelling under a nominal surcharge pressure. As swelling is not permitted in Method B and C, the original fabric remains the same.