Estimating Optimum Water Content and Maximum Dry Unit Weight for Compacted Clays

An empirical method is described for estimating maximum dry unit weight (γdmax) and optimum water content (wopt) of clayey soils at any rational compactive effort E. One variation of the method uses the liquid limit (LL) and one compaction curve, whereas the other uses only the LL. Linear relationships between γdmax and the logarithm of compaction energy (log E), and wopt and log E, both of which are a function of the LL, are used to extrapolate to different compactive energies. Data for 22 clayey soils were used to develop the method, and data for five additional soils were used for validation. Both variations of the method are unbiased and robust. The variation employing the LL and one compaction curve is slightly more precise, with typical errors of about ±1% for wopt and ±2% on γdmax. For the variation employing only the LL, typical errors are about ±2% for wopt and ±6% on γdmax.