Evaluation of swelling-shrinkage of expansive soil based on subjective and objective weighting and efficiency coefficient methods

Objective Classifying the swelling-shrinkage degree of expansive soil is a critical issue in their management of expansive soil. To prevent and mitigate engineering disasters, accurate evaluation of the swelling-shrinkage for expansive soil is essential. This study applies the efficacy coefficient method to classify the swelling-shrinkage grade of expansive soil. Methods Five factors(the liquid limit, total swell-shrink ratio, plastic index, water content, and free swelling ratio) are selected as evaluation indices to comprehensively assess the swelling-shrinkage characteristics. The weight coefficients of these indices are determined using both objective and subjective weighting method, namely the Delphi method and information entropy theory. The final classification is obtained by calculating the total efficacy coefficient of the sample. A new model for evaluating the swelling-shrinkage grade of expansive soil is established using the efficacy coefficient method in combination with the subjective and objective weighting approach. The model is tested on 19 sets of field test data from relevant literature, with 15 groups of data compared to other methods and 4 groups of data compared to actual situation. Results The accuracy of the model, when compared with extension theory, the variable weight and the unascertained measurement method, reached 93.3% for the 15 groups of data. For the 4 groups of data compared with the real-world conditions, the accuracy reached 100%. Conclusion The proposed model is both reasonable and effective in classifying the swelling-shrinkage grade of expansive soil, offering valuable guidance for the safe construction of expansive soil projects.