Novel analytical methods for predicting the response of bored piles in sand-Paper

Paper

Pdf Summary

The paper presents physically based methods for predicting the axial load–settlement response of bored piles in sand using soil parameters obtainable from standard site and laboratory tests.<br /><br />For pile-base resistance, the authors model pile-tip penetration by analogy with expansion of a spherical cavity in an elasto-plastic soil. They use the Yu and Houlsby cavity-expansion solution and relate cavity pressure and expansion to base stress and settlement. The model accounts for sand stiffness and strength and was assessed against a database of 50 full-scale pile tests, with reported agreement across different pile geometries and installation methods.<br /><br />For shaft resistance, the proposed framework accounts for increased horizontal stress caused by soil dilatancy within the shear band around the pile. It estimates the ultimate shaft friction from soil stiffness, dilation, particle size, and shear-band properties. Shaft load–settlement behaviour can then be represented using a hyperbolic or more flexible load–settlement relationship. Comparisons with five full-scale tests provide a further check of the approach.<br /><br />The base and shaft responses are calculated separately and combined to estimate the pile’s total response. Fleming’s method can also be used to account for elastic shortening of the pile, which is neglected under a rigid-pile assumption. Overall, the methods offer a practical alternative to empirical design rules, while emphasizing that reliable prediction of the single pile’s response is central to foundation design and settlement-based capacity assessment.

Keywords

bored piles

sand

axial load-settlement

cavity expansion

pile-base resistance

shaft resistance

soil dilatancy

elasto-plastic soil

full-scale pile tests

pile settlement prediction