Estimation of unimodal water characteristic curve for gap-graded soil

Soils with a bimodal grain-size distribution (gap-graded soils) can be associated with unimodal or bimodal soil-water characteristic curves (SWCCs). Many equations have been developed to estimate SWCCs using grain-size distribution curves to overcome the high cost and long duration of SWCC experiments. Most of the equations are limited to the estimation of the SWCCs of soils with a unimodal grain-size distribution. Few studies have been conducted on the estimation of unimodal SWCCs for gap-graded soils. In this paper, procedures, equations and computer codes are proposed for estimating the unimodal SWCCs of gap-graded soils. The proposed equations are found to perform well in estimating the unimodal SWCCs of gap-graded soils.