A new double structure model for expansive clays

Abstract

The behaviour of compacted bentonite upon hydration is n umerically investigated here by simu- lating a swelling pressure test on a MX - 80 bentonite sample . Two constitutive models are employed in the analysis : the “Imperial College Single - Structure Model” (ICSSM) and the “Imperial College Double - Structure Model” ( ICDSM), the latter specifically developed for expansive clays. It is shown that the latter exhibits a considerably improved performance as it is able to accurately capture the swelling pressure developed in the material upon wetting . Nevertheless, a limite d knowledge of the evolution of the material’s fabric, notably at the micro - scale, is an obstacle for deriving with certainty some of the model parameters . This issue is high- lighted here by performing analyses of the swelling pressure test with two sets of material characterisations, with model parameters differ ing i n the derivation of the microstructural component . B oth analyses show a very good match with the test data , but it is difficult to justify one set of microstructural parameters over the other. T he paper emphasises what aspects of experimental research could be helpful in studying the fabric of compacted bentonite upon wetting, and hence improve the calibration procedure of the double - structure mod- el.