Abstract: The comparative compression tests were performed on the natural sedimentary undisturbed clays and corresponding remolded samples. The test results indicate that the destructuration after gross yield is a progressive process; the post-yield compression curve displays a nonlinear behavior in the plot of ; and the compression index, Cc, designated by the slope of the curve, is not constant in the entire stress range, which cause trouble to settlement calculation. Therefore, the double logarithmic coordinates system is used to represent the compression curve. A good linear relationship between the logarithm of the specific volume and logarithm of consolidation stress is obtained for clays with different initial structures. The soil structural yield stress and compression indices in the pre-yield and post-yield phases are effectively and simultaneously determined. And then taking into account the sample disturbance, a method of modifying the compression parameters is presented to predict the virgin compression curve; and a bilinear compression model is developed for the structured clays. Based on the experimental data in this paper and other literatures, the empirical relationship between the yield stress and undrained strength, and relationship between compression index and stability index (SI) as well as liquid limit (wL) are established. This study results provides a reasonable basis for determining the consolidation and settlement calculation parameters.

Key words: soil structure, in-situ compression curve, bilinear model compression, structural yield stress, compression index