Abstract
The compression index Cc for undisturbed clays which is one of the mechanical properties of soils must be expressed as a function of three kinds of factors, which are type of soil, condition of soil and structure of soil.
Now by selecting plasticity index Ip, liquidity index IL and sensitivity ratio St as representatives of these three factors and expressing the effect of contributions of both Ip and IL to Cc by the multiplication of Ip and IL {Ip × IL= (w0-wp)}, Cc can be expressed as
Cc=F {(w0-wp), St}
where w0 and wp are initial water content and water content at plastic limit, respectively.
The above mentioned function for Cc was examined in its applicability to undisturbed clays and the following Cc equation was obtained: Cc/St0.22=0.009 (w0-wp) + 0.101 (regression coefficient, r=0.911).
Comparing the Cc equation shown above with the Cc' equation previously obtained for disturbed clays, the ratio, Cc/Cc' was expressed simply as a function of only St in the range of Cc > 0.4 as, Cc/Cc' = 1.25 St0.22.
