Soil-Water Characteristic Curves of Stabilized Expansive Soils

TLDR

Expansive soils are conventionally improved with additives such as fly ash, lime, or chemical additives, and are commonly referred to as stabilized, modified, or treated soils. The study uses SWCC data to interpret the behavior of stabilized expansive soils and to extend this understanding to other similar soils. SWCCs of two Texas expansive soils were measured in natural and stabilized states with a pressure plate apparatus (0–1,000 kPa), and multiple linear regression linked basic soil and stabilizer properties to Fredlund–Xing model constants. Using six independent soil properties yields higher correlation coefficients, and the predicted volumetric water contents agree with measurements within ±20% for ash‑treated soils and ±15% for ash‑plus‑fiber‑treated soils.

Abstract

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 ±20% for ash-treated expansive soils, and within ±15% for combined ash- and fiber-treated 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.