Soil-Water Characteristic Curves of Stabilized Expansive Soils

The engineering properties of expansive soils are conventionally improved through the use of additives such as fly ash, lime, and chemical additives. Such soils are often referred to as stabilized or modified or treated expansive soils. The soil-water characteristic curves (SWCC) of two expansive soils from Texas were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-1,000 kPa. The SWCC results are used to interpret the expansive soil behavior due to stabilizer treatment. In addition, relationships were developed between the basic soil and stabilizer properties such as water content, dry density, liquid limit, plastic limit, and stabilizer dosages and the model constants of the SWCC formulation of Fredlund and Xing via multiple linear regression analysis. The analysis showed that higher coefficients of correlations can be achieved by using six independent soil properties. The comparisons between the predicted and measured volumetric water contents are within (plus-minus) 20% for ash-treated expansive soils, and within (plus-minus)15% for combined ash- and fibertreated expansive soils. The research data and interpretation analysis presented here can be extended to understand volume change behaviors of other stabilized expansive soils using the SWCC test data.