Behaviour of skirted footings on sand overlying clay

Abstract

On sand overlying soft clay, the bearing resistance developed in the upper soil layer could be substantially larger than that in the lower layer. Installing an offshore foundation on this kind of soil condition could possibly bring about punch-through risk when the imposed load exceeds the upper soil bearing resistance. Intuitively, the punch-through risk could be reduced by minimizing the bearing resistance variance between the upper and lower layers by either reducing the bearing resistance of the upper soil or increasing bearing resistance of the lower soil. The former case is explored in this paper by adopting a footing with extended skirt denoted as skirted footing. This paper reports the findings obtained from a series of centrifuge model tests to investigate the effect of skirt height on the development of bearing resistance of skirted footings in sand overlying clay. The findings suggest that skirted footings produce a lower peak bearing resistance and punch-through depth as compared to spudcan foundation. The footing with skirt height equaling the sand thickness appears to greatly reduce the risk of punch-through failure. © 2011 Taylor & Francis Group, London.