Abstract
This paper presents the development of load-transfer curves that can be used to estimate the displacement under axial load of driven piles in sand. The maximum skin friction and end-bearing stress are obtained from new ISO 19901-4 cone penetration test (CPT)-based formulations, which were calibrated using a high-quality database of static pile load tests compiled for this purpose. The load–displacement responses measured in the 71 static load tests in this database are used to derive CPT-based non-linear load-transfer curves. It is shown that good estimations of pile displacements can be obtained using CPT data and the normalised formats of shaft and base load-transfer functions provided in the American Petroleum Institute and ISO 19901-4 recommendations.
Highlights
A joint industry project (JIP) was set up in 2013 by the Norwegian Geotechnical Institute (NGI) to examine the reliability of a range of existing methods employed for evaluation of the axial capacity of driven piles in sand
To assist with this aim, the University of Western Australia (UWA) together with NGI compiled a database of highquality pile load tests in sand and clay, which is referred to as the ‘Unified’ database (Lehane et al, 2017)
Full details of the database are provided in Lehane et al (2017), which examines the ability of existing cone penetration test (CPT) methods to predict pile capacity
Summary
Unified method for calculation of axial capacity The derivation of load-transfer curves requires definition of the ultimate shaft friction that can develop at any location on the pile shaft (τf) and the ultimate end-bearing stress acting over the full pile base area at a displacement of 10% of the pile diameter (qb0·1). Two preliminary exercises assisted with establishing a correlation for this ratio: Correlations were explored that would minimise the difference between the measured and calculated Q–δh responses of the database piles for loads that were less than 50% of the ultimate capacity (Qult) – that is within the typical working range.
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