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SUCTION – VOLUME CHANGE COEFFICIENTS
OF EXPANSIVE CLAY MINERALS
The suction-volume change coefficients of expansive soils can be found from the
following charts and some simple calculations.
Step 01.
Find where the soil plots on the Plasticity Chart (pages 2 and 3). Find which zone (I
through VI) it falls into.
Step 02.
Go to the figure that shows the soil compression index values for 100% fine clay (Figures
1 through 6 corresponding to zones I through VI). Interpolate between the contours to
find the value of γ100. The vertical axis is (LL / percent fine clay) and the horizontal axis
is (PI / percent fine clay).
Step 03.
Calculate the suction compression index for the soil by
γh = γ100 x (percent fine clay)
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