Mike Long, University College Dublin, Paul Quigley, Irish Geotechnical Services and Peter O’Connor, APEX Geoservices. This paper was first published in GE’s November 2013 issue.
Much of the ground engineering work carried out in Ireland involves glacial tills. These tills were deposited beneath the ice sheet that covered much of Ireland during the Pleistocene period, some 18,000 years ago. For example, much of the city of Dublin it is underlain by a glacial deposit known colloquially as Dublin boulder clay (DBC).
It is known that the ice thickness in Dublin was approximately 1km and that several advances and retreats of the glaciers occurred in the area. The grinding action of this sheet as it eroded the underlying rocks coupled with its loading effect resulted in the formation of a hard lodgement till which in engineering terms is characterised by being very dense/hard, of very high stiffness and of low permeability.