Shaft Capacity of Displacement Piles in Clay Using the Cone Penetration Test: Fid-Bau Portal

Shaft Capacity of Displacement Piles in Clay Using the Cone Penetration Test

Lehane, Barry M. / Li, Yunong / Williams, Ryan

Abstract

The prediction of the shaft capacity of displacement piles in clay still relies wholly on empirical or semiempirical approaches. This paper examines the predictive abilities of five well-known methods against an extended version of an existing database of pile tests. It is seen that coefficients of variation (COVs) of the ratio of calculated to measured capacities ( $Q_{c} / Q_{m}$ ) are significantly higher than expected. The paper then uses the database of shaft capacities to examine potential relationships between local shaft friction and the cone penetration test end resistance ( $q_{t}$ ). Predictions are subsequently compared with capacities measured in a series of centrifuge tests and with the distributions of peak frictions observed in two well-documented field tests. Widely different formulations adopted by each of the existing empirical methods give broadly similar COV values for $Q_{c} / Q_{m}$ ratios, and it is concluded that the database of high-quality pile tests needs to be expanded significantly if the reliability of estimates of shaft capacity in clay is to be improved.