Mechanisms controlling compressibility of clays

The consolidation characteristics of clays are controlled by mechanical and physico-chemical effects. Although these effects operate simultaneously one-dimensional consolidation tests indicate that one or the other usually dominates. The consolidation characteristics of sands, mica, and kaolinite are mechanically controlled whereas those of smectite are physico-chemically controlled. Illite occupies an intermediate position in that the virgin compression curve seems to be controlled by mechanical variables, whereas the swelling curve is influenced by both effects; the physico-chemical effect is more important when the adsorbed cations are monovalent and the pore water electrolyte concentration is low