The impact of hydrogeology on the instability of a road cutting through a drumlin in the North of Ireland

D. A. B. Hughes, G. R. T. Clarke, R. M. G. Harley, S. L. Barbour

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    5 Citations (Scopus)
    295 Downloads (Pure)

    Abstract

    This paper describes the hydrogeological processes which caused unexpected instability and quick conditions during the excavation of a 25m deep cutting through a drumlin in County Down, Northern Ireland. A conceptual hydrogeological model of the cutting, based on pore pressures monitored during and after the excavation demonstrates how quick conditions at the toe of the cutting caused liquefaction of the till. Stability of the cutting was re-established by draining the highly permeable, weathered Greywacke which underlies the drumlin, through the use of a deep toe drain. In spite of this drainage, the cutting was only marginally stable due to the presence of a low permeability zone in the till above the bedrock which limits the reduction of elevated pore pressures within the upper to mid-depths of the drumlin. The factor of safety has been further improved by the addition of vertical relief drains at the crest and berm of the cutting to relieve the pore-pressures within the upper till by intercepting the weathered bedrock. The paper also highlights the importance of carrying out an adequate site investigation compliant with Eurocode 7 and additional monitoring in excavations in stiff, low permeability till.
    Original languageEnglish
    Number of pages13
    JournalQuarterly Journal of Engineering Geology & Hydrogeology
    Early online date09 Feb 2016
    DOIs
    Publication statusEarly online date - 09 Feb 2016

    Keywords

    • Geotechnical Engineering; Roads and Highways; Site Investigation.

    ASJC Scopus subject areas

    • Engineering(all)
    • Civil and Structural Engineering

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