Effect of Destructuration on the Compressibility of Perniö Clay in Incremental Loading Oedometer Tests

Abstract

The paper evaluates the destructuration and creep properties of soft sensitive Perniö clay during one-dimensional consolidation. Incremental loading oedometer tests presented herein were part of an extensive testing program performed on natural and reconstituted samples of Perniö clay. Given the experimental results, general stress–strain compression curves were investigated taking into consideration the effects of clay structure and sample quality. The effect of sample disturbance on preconsolidation pressure was quantitatively evaluated by an exponential relationship. Compression parameters accounted for the detailed stress-dependent behavior. The assumption that the Cae/Cc ratio would be constant in one-dimensional consolidation was proven wrong. Three new sensitivity approaches were developed and proved to be feasible in comparison with sensitivity determined by fall cone tests. The developed sensitivity indices were exponentially related to the initial void ratio e0. The stress–strain–strain rate isotaches were plotted to explore the gradual destructuration process at different strain rates. For Perniö clay, the v−σv′ isotaches coupled with strain rates were neither parallel in linear nor natural logarithmic scale. Special attention was given to the tangent modulus theory, which was used to analyze the complete destructuration process of natural clay. The defined characteristic parameters were interpreted, taking into account sampling depth and sample quality.