The Distribution and Engineering Properties of Interglacial Deposits in Cork City and Harbour

Abstract

A reassessment of existing data and additional testing on sediment core samples from one site was used to study the extent, nature, composition and engineering properties of the Quaternary interglacial deposits in an area of Cork city and harbour where many future developments are planned. A clear link is apparent between rockhead elevation and the presence of the interglacial deposits. Well-defined pockets of the deposit were proven. These are found mostly on the southern side of the Cork buried valley axis and increase in thickness to the north. The base of the interglacial deposits appears to mirror that of the rockhead and the western extent of the former coincides with a steep drop off in the latter. Much of the deposit encountered in commercial investigations is a thick relatively uniform silt/clay consistent with that described in previous studies. The sediment is predominantly silt sized, but its behaviour and engineering properties are consistent with those of a stiff clay. Sample disturbance effects were found to be significant and these likely result in an underestimation of the preconsolidation stress and the undrained shear strength of the material. Future work would benefit from the use of in-situ site investigation and geophysical techniques.