Abstract: Identification and classification of expansive soils are the main tasks that should be firstly solved in constructions in regions occurring expansive soil.Based on previous studies,in this paper we choose four indices,namely,liquid limit,plastic limit,degree of free swelling and standard moisture absorption water content of soil.They are usually involved in the classification of expansive soils.The significance of the above four indices is evaluated using the rough sets theory.According to the s...