Study of the structure of a sensitive Champlain clay and of its evolution during consolidation

Scanning electron microscopy and mercury intrusion porosimetry are used in parallel to identify the structure of a medium sensitivity Champlain clay. The clay structure is observed firstly on intact, remolded, and oven-dried soils and secondly on soils consolidated at various levels in one-dimensional compression. Both methods of investigation reveal for the intact soil the existence of an aggregated structure characterized by an interaggregate and an intra-aggregate porosity. Remolding affects interaggregate links but does not destroy aggregates.The observation of clay structure at various levels of one-dimensional compression shows that the collapse of the structure is progressive, the largest interaggregate pores being the first affected. As the consolidation proceeds, smaller and smaller pores are affected. For a given pressure increment, only the largest existing pores are affected. A structure anisotropy has been seen to develop with increasing compression.The scanning electron microscope and the mercury intrusion porosimeter used in conjunction with each other appear as a powerful approach for clay structure observation. Keywords: natural clay, microstructure, freeze-drying, porosimetry, microscopy, consolidation, aggregate.