The geotechnical implications of the inherent complexity of glacial sedimentary sequences have been recently emphasized and it has been suggested that more extensive use be made of engineering geological and geomorphological mapping, especially in the preliminary stages of site investigations. The incidence of certain geomorphic processes beyond the ice margins, notably periglacial solifluction, obscures the relationship between glacial depositional landforms and glacial deposits, especially when periglacial activity has prevailed throughout a glacial period. In such a case, the level of discrimination and sophistication required of these techniques is higher than that demanded using a‘land system’ approach in ice-moulded terrain such as that of the last (Devensian) glaciation.
This paper describes examples from the east Midlands of England, where recent engineering operations have encountered serious difficulties due to complex glacial assemblages or unstable bedrock being found beneath apparently simple morphostratigraphic surfaces. Surfaces mapped, for example, as late Tertiary‘erosional platforms’ and late Pleistocene river terraces can be shown to be the product of periglacial processes.
Examples are described from recent engineering projects and suggestions are presented as to how similar problems may be avoided in the future.