Volume 40, Issue 2 (March 2012)
Recent Developments in the Swelling Model of Expansive Clays for Pavement-Heave Calculations
The prediction of pavement heave necessitates knowledge of the swelling-pressure characteristic (the swelling model) of the clay stratum under consideration, data that are usually obtained from laboratory tests on undisturbed clay specimens. It is demonstrated that a general swelling model equation should be employed that predicts the percentage of swell under a given vertical pressure exerted on clay characterized by the following parameters: (a) the liquid limit, (b) the ratio between the in situ moisture content and the plasticity limit, and (c) the in situ dry density. The development of this general equation is described by applying the Excel-solver analysis to 352 local test results, yielding preferable results to those stemming from a previous analysis that utilized the multiple linear regression method. Together with employing the general swelling model, an adjustment for any specific given condition is performed by conducting linear regressions (a simple one and a zero-intercept one) with the local test results and the general swelling model. Finally, the paper outlines guidelines for choosing the most relevant of the three calculated models.