Classification procedures for expansive soils

Abstract

Most of the national codes of practice do not give characterization and classification of expansive soils, in spite of expansive soils being distributed very widely over almost all geographical locations in the world, causing distress to the structures founded on them and discomfort to the users. A simple user-friendly approach based on the free swell ratio, defined as the ratio of the sediment volume of soil in distilled water to that in carbon tetrachloride or kerosene, is formulated considering the compatibility of the results with oedometer free swell tests and the soil clay mineralogy. Statistical illustrations are provided which clearly indicate that while the assessment of soil expansivity based on index properties is an overestimation, there is a consistency in the classifications based on oedometer test results and the proposed approach. It is recommended that simple approaches such as the one proposed here to classify the expansive nature of soils are entered into standard codes of practice.