Identification of Expansive Soils and Assessment of Expansion Potential by Fuzzy Approach

Expansive clayey soils are highly moisture sensitive with respect to stress, deformation and strength. These soils exhibit extreme variation in deformation such as heaving, loss of shear strength under certain Moisture Content and settlement and shrinkage as the Moisture Content alters. Swelling is the process of increase in volume of soil that occurs during its interaction with water. Expansive soils are classified based on Expansion Potential. Estimation of Expansion Potential serves as a guide for safe analysis and design of structures resting on expansive soils . Expansion potential is dependant on mineralogical composition of soil which influences the index properties of soil. Several investigators proposed criteria for qualitative assessment of Expansion Potential making use of index properties of soil .Uncertainties arise in making use of these criteria, since the soil properties cannot be used separately but collectively to assess Expansion Potential. These soil properties are fuzzy rather than Crisp. This paper presents a Fuzzy Rule Based Approach using fuzzy IF-THEN rules to quantify the Expansion Potential in qualitative terms considering the index properties of expansive soils and expanding clay minerals. Fine Fraction, Liquid Limit, Shrinkage limit, Plasticity Index and Free Swell Index are used as Linguistic and numeric input variables. The output is Expansion Potential in quantitative terms determined from the fuzzy output membership function using Mandani Fuzzy Inference.