Shear Strength and Compressibility Behavior of Bhavnagar Expansive Soil with Varying Mineralogical and Swelling Properties

Expansive soils contain large amount of montmorillonite clay mineral; which have tendency to swell by imbibing water in monsoon season & shrink or become harder by leaving cracks in drier seasons. Excessive drying and wetting of the soil progressively deteriorates structures over the years and cause severe damage particularly to the light buildings, and pavements either through heave or differential settlement. Limited research has been reported regarding the identification of expansive soils and determination of its expansiveness & shrinkage-swelling potential based on soil’s different index properties at various wetting-drying conditions. Few researchers also worked on the chemical stabilization of expansive soils by mixing various admixtures and evaluated the method for improvement in soil’s mechanical behavior in terms of volume stability, strength response, permeability and durability. The fundamental understanding of expansive soil in terms of relationship of its mineralogical properties, swelling parameters, consistency limits, compressibility, and shear strength parameters are still unexplored. The current research has been performed on expansive soil (black cotton soil) covering major part of Bhavnagar, located along the coast line of Gulf of Khambhat in Gujarat. This research is focused on the evaluation of mineralogical properties, swelling-shrinkage potential, consistency limits, compressibility and shear strength response of expansive soils collected from ten different locations of Bhavnagar. X-ray diffraction (XRD), cation exchange capacity (CEC), and specific surface area (SSA) tests were performed on Bhavnagar expansive soil to identify its minerlogical properties at differnt locations. A series of 1D consolidation and UU triaxial tests were performed on ten soil samples to evaluate the compressibility and shear strength properties of Bhavnagar soil. This extensive experimental research work has been used to develop the mathematical correlations for expansive soils to predict the compressibility and shear strength behaviour of soil based on its mineralogical parameters, swelling properties and consistency limits.