Evaluation of expansivity of Neogene clays and glacial tills from cental Poland (Warszawa area) on the basis of suction tests

This paper presents the characteristics of the expansivity and quantitative prediction of heave of clay soils from Poland based on suction testing. Eleven Neogene clays and six glacial tills, differing in genesis and plasticity, were analysed to identify the expansive potential using eight empirical methods. The laboratory studies included measurements of soil-water characteristic curves and soil index properties. Data from water content, volume and suction measurements served to determine the suction compression index Ch and the suction-water content index delta h/delta w of the soils examined. The values of these indices are clearly dependent on the clay fraction content in tested soils. Compared with glacial tills, Neogene clays are expected to exhibit greater changes in volume due to changes in soil suction. Comparative results of the evaluation of expansivity suggest that the chosen classification methodologies provided consistent expansion ratings for glacial tills, while the values for Neogene clays vary from low to very high. The lowest expansivity classes have been obtained from evaluation based on soil suction. The McKeen (1992) method has been adopted for calculations of the potential field heave of Neogene clays and glacial tills. In order to provide a rational estimation of expansive soil behavior, specialists should take into consideration the specific site and design features.