Abstract

Historically only shallow basements were included in developments in Cork city owing to the underlying layers of soft alluvium and high-permeability glaciofluvial gravels. In recent times several large schemes, with basements up to 10 m deep, have been completed. In this paper the design and performance of these developments is summarized. Particular emphasis is placed on two schemes at Eglinton St. and Half Moon St. Although dewatering by deep well systems is feasible, flow rates can be substantial. Careful consideration needs to be given to the site-specific properties of the glaciofluvial gravels to permit the level of the cut-off to be efficiently chosen so as to minimize inflows and external groundwater lowering and to mitigate against the possible risk of surface settlements. A ‘soft gel’ grout blanket was used successfully as an alternative at one site. Lateral wall movements were low and it seems possible that more efficient designs are possible, especially if the small strain stiffness and dilation properties of the material are taken into account.

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