A Coupling Model for Shrinkage-Swelling Classification of Untreated and Lime-Treated Expansive Clay

Classification of shrinkage-swelling grade of untreated and lime-treated expansive clay is of importance for stability and safety of airport runway founded on expansive soils. Herein, a novel model for classification of shrinkage-swelling grade was proposed by means of coupling rough set (RS) theory and set pair analysis (SPA). Based on measured values of evaluation indexes, rough set theory was used to conduct attribute reduction. And the weights of residual evaluation indexes were specified according to the attribute importance. Moreover, a concept of connection number for a set pair, which consists of measured evaluation index sets and classification standard sets of shrinkage-swelling grade, was described to express hierarchy and fuzziness of membership to a shrinkage-swelling grade. Combined with weight of evaluation index, integrated connection number was calculated to specify shrinkage-swelling grade of evaluation samples. Finally, a practical example of runway foundation treatment in Hefei international airport was used to verify this proposed method. Comparing with the fuzzy mathematics method and variable fuzzy set method, this presented method is more feasible and easy to operate.