The influence of soil slip on negative skin friction in pile groups connected to a cap

Abstract

INTRODUCTION There have been several investigations into the behaviour of isolated piles in groups subject to negative skin friction (NSF), from experimental observations and theoretical studies (Shibata et al., 1982; Jeong et al., 2004; Lee & Ng, 2004). However, to date, the behaviour of piles in groups connected to a cap in consolidating soil has attracted less attention among engineers than the study of isolated piles in groups. There is only a limited number of relevant case histories on the behaviour of piles connected to a cap (Chellis, 1961; Garlanger & Lambe, 1973). These authors have reported the development of tensile forces in the outer piles, leading to pulling of the outer piles from the pile cap in some cases. Kuwabara & Poulos (1989) and Chow et al. (1996) reported distributions of axial forces along piles obtained from elastic solutions using Mindlin’s elastic theory. They showed the development of tensile forces in outer piles near the pile head. It is well known, however, that by ignoring soil slip at the pile/soil interface the elastic solution resulted in an unrealistic estimation of pile behaviour under the influence of NSF (Jeong et al., 2004; Lee & Ng, 2004). Therefore, in this study, a series of three-dimensional (3D) numerical analyses, including soil slip, was conducted to clarify the behaviour of piles in groups connected to a cap.