Pore Sizes and Strength of Compacted Clay

Pore size distributions, compaction characteristics, and undrained strength and deformation data were related in tests to molding water content and type of laboratory compaction. The soil used was the commercially available illite clay called Grundite. Pore size distribution measurements, carried out by mercury porosimetry, require dry samples. Removal of the water with small to negligible volume change is possible by freeze drying. The pore size distribution measurements were obtained, after freeze drying, for a diameter range of about 600 /fgm/fgt to approximately 0.016 /fgm/fgt. Samples compacted at moisture contents less than the Proctor optimum moisture contents showed brittle compressive failures at low strains, apparently due in part to the breakdown of numerous larger pores. Samples compacted wet of optimum moisture contents continued to deform to high strains.