The 1st Hanrahan Lecture: Geotechnical properties of Irish glacial and interglacial soils

Abstract

This paper reviews the current state of the art in relation to geotechnical design in unsorted till deposits, commonly called boulder clays by engineers or diamictons by geologists, generally taking the topics discussed by Professor Eamon Hanrahan in his seminal work of 1977 on Irish tills. These topics include the permeability, stiffness and consolidation characteristics of these deposits, together with their undrained and drained behaviour. The geological background to the deposition of these tills is discussed and the available information on the presence of interglacial soils around the country is presented. Where possible, practical experience from working with these deposits is compared with predictions made from field or laboratory test results: for example, in settlement assessment of foundations, slope stability and in earthworks. Whilst most of Ireland is covered with stony boulder clays, which is the main topic of this paper, the geotechnical parameters of a fine-grained till encountered on the east coast, known as Irish Sea Till or colloquially as Macamore Clay, are discussed and the implications of this on slope stability is investigated.