Assessment of testing method influence on swelling characteristics of expansive soils of India

Many studies have highlighted the role of mineralogy, chemical parameters, and testing methods influence on the swelling behavior of expansive clays. However, studies available in the literature pertinent to testing methods effect on swelling property are extremely limited. Testing methods such as 1-D consolidometer, constant volume, swell-reload, and load back pressure have been developed by the research fraternity. In the present study, several expansive clay samples were collected from different locations across India, and swelling properties of these soils were measured by employing the above four methods. Correlations for montmorillonite content and chemical parameters versus swelling property measured by four methods are derived, additionally. Such an attempt is of great interest to researchers to understand the performance of these methods when considered soil types belonging to same region. Furthermore, numerical analysis to check the expansive clays suitability, by giving obtained swelling properties as input data, for shallow (square footing) and deep foundation (under-reamed pile) systems is assessed. Among four methods, it is found that 1-D consolidometer method yields conservative values of swelling property, while constant volume method yields lowest S p of soils belonging to same region. The results postulate that an inherent variation in S a and S p with a change in testing method is obvious. Results demonstrate that both micro-level parameters and testing methods, which in turn showed strong dependence on former parameters, have a definite influence on the swelling characteristics of soils. Numerical analysis results reveal that a shallow foundation is highly unsuitable as safe bearing capacity is confined to 100 kPa while adopting a deep foundation system that ensured a minimum safe bearing capacity of 500 kPa is essential. Based on the outcome of the study, it is advocated to rely on prevailing site conditions to select the testing method and type of foundation system.