Modelling of Swelling Parameters and Associated Characteristics Based on Index Properties of Expansive Soils

Presence of swelling soils under the foundations of civil engineering structures particularly lightly loaded structures has caused serious damages around the globe due to their differential up heaving. In this paper, based on the results of swell tests on bentonite mixed clay, correlations for predicting the swelling parameters (i.e., swell potential and swell pressure) have been proposed. Mixing of bentonite into low swelling clay has imparted significant variations in its index properties including activity and plasticity index as well as in its swell potential and swell pressure values. Mixing of bentonite from 0 % to 55% into lean clay (CL) varies its placity index value from 18 to 150 resulting into variation of its activity from 0.62 to 1.87. For the same range of bentonite addition, the swell potential and swell pressure values vary from 2.62% to 12.16% and 94 kPa to 928 kPa, respectively. Based on multiple linear regression analysis of swell and index property test data, correlations between swelling parameters, activity and remolding moisture content for expansive soils have been developed. Experimental data of twenty six (26) swelling soils procured from various sites in Pakistan have been used to validate the proposed correlations. These correlations have predicted the swell potential and swell pressure of these soils within accuracy of +10% and +5%, respectively, in comparison with their experimentally determined values. A comparison of these predictions with couple of well-known published empirical equations has also been made.