Predicting the Behaviour of C.F.A.
Piles in Boulder Clay

 

Myles Lawler

Formerly Ph.D. researcher at Department of Civil Engineering,
University of Dublin (Trinity College), Dublin, Ireland
e-mail

ABSTRACT

This paper presents an assessment of the ability of a soil model with potential commercial application, called the Hardening Soil model, to predict the behaviour of an instrumented Continuous Flight Auger (C.F.A.) pile in the stiff (glacial) till, found in Dublin (Ireland) when used in a finite element analysis. The model incorporates many of the decisive features of the stiff glacial soil, including the highly non-linear stress-strain response and the strong stress dependency of stiffness. It is shown that the model underestimates pile settlement in the wished-into-place case. However, measured and predicted pile settlements were found to be in good agreement when pile construction effects were taken into account. This is due, in part, to the correct prediction of the combination of high shaft friction and relatively low end bearing mobilised in the pile but also to the relative simplicity of C.F.A. pile construction, vis--vis standard bored piling.

Keywords: boulder clay, C.F.A. piling, soil modelling.

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