Surcharged embankments over peat in north-west Ireland: primary consolidation behaviour

This paper presents selected data relating to the primary consolidation of blanket peat under surcharged embankments on a road improvement scheme in Co. Donegal, Ireland, completed in 2022. The back-calculated compression index was found to be compatible with values for Scandinavian peats and in keeping with a well-known empirical prediction at equivalent moisture contents. Coefficients of consolidation, derived using Asaoka final primary consolidation settlements as the starting point, exceeded those inferred from piezometer data, but both values significantly exceeded oedometer-derived values at equivalent effective stress levels. Carlsten’s (1988) method produced a reasonable estimate of time to 90% consolidation once used within the intended loading range. A particular focus of the paper is on the corrections/assumptions necessary to interpret primary consolidation parameters in large strain scenarios.