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Expansive clays and Tezaghi effective stress

Experimental data on nine different sodium and calcium bentonites from literature are examined. Specific experiment types are selected so that we evaluate the behaviour of microstructural units (aggregates) rather than the global behaviour of compacted bentonite, which is influenced by its double structure. We show that it is possible to uniquely represent the unconfined water retention curve, swelling pressure tests, swelling under constant load tests and mechanical unloading tests in the space of dry density of clay aggregate vs. mean Terzaghi effective stress. Our analysis implies that the Terzaghi effective stress is applicable for description of the expansive clay aggregate behaviour and it is reasonable to consider the behaviour of aggregates to be reversible. In addition, for a broad range of suctions, they can be considered as fully saturated.

Author(s):

David Mašín    
Charles University in Prague
Czech Republic