Back calculated α and β coefficients from case histories of negative skin friction piles

Abstract

This paper presents the back calculated α and β coefficients from case histories in negative skin friction piles and provides an engineering reference for engineers to design a negative skin friction pile. Negative skin friction or dragload is a common problem for a pile in a highly compressible soil. There are mainly two methods to calculate negative skin friction: α and β methods. In this paper, α and β coefficients are back calculated based on several known case histories. It is found that both α and β coefficients vary in a wide range. The average values of 0·62 for α and 0·21 for β are recommended for uncoated piles compared to 0·17 and 0·07 for α and β for coated piles.

Keywords:

• Negative skin friction
• Pile
• Case history
• Back calculation
• α and β coefficients

The authors want to acknowledge the scholarship awarded to the first and fourth authors by the China Scholarship Council during their 1 year study at Ryerson University. Financial support from the Natural Science Foundation of Jiangsu Province, China for this research under Grant No. BK2008040 is gratefully acknowledged.