Abstract

Piles driven in clay are often subjected to indirect loading as a result of the surcharge applied on the surrounding area. During the drained period, both the pile and the soil undergo downward movements caused by the axial and the surcharge loading, respectively. Depending on the relative movement of the pile/soil system, positive and negative skin friction develop on the pile's shaft. Negative skin friction is the drag force that may be large enough to reduce the pile capacity and/or to overstress the pile's material causing fractures or perhaps structural failure or possibly pulling out the pile from the cap. A numerical model was developed to simulate the case of a single pile driven in soft clay layer overlying a deep deposit. Coupled consolidation method of analysis is adopted to predict time/settlement/skin friction distribution relationships. The model is an axisymmetric that uses the finite element technique combined with the soil responses according to Mohr-Coulomb criteria. The model was first tested against the results predicted by the classic theories for bearing capacity of pile foundations on clay. Furthermore, the model was validated with the results of three full scale field tests available in the literature