The Performance of Road Embankments on Glacial Deposits in Ireland

AbstractGlacial deposits are very common as foundation soils supporting road embankments in Ireland and are typically present in almost all road projects. Despite this there is limited research data linking the settlement performance of embankments to the compressibility and consolidation properties of such soils. This is largely due to the difficulties in obtaining representative, high quality undisturbed samples and laboratory testing of glacial deposits, which exhibit a large range of gradation particle sizes including gravels, cobbles and boulders.The paper presents the results of several case histories of foundations and monitored road embankments supported on glacial deposits located throughout Ireland. In situ field compressibility and consolidation parameters are back calculated from field performance and correlated to standard index properties such as liquid limit, plasticity index, particle size gradations and SPT N values. Some general conclusions plus recommended ways to predict embankment performance from commonly obtained geotechnical test data are suggested. Identification of difficult glacial soil types requiring special investigation and treatment or improvement are suggested