Numerical Simulation and Parametric Study of a Single Pile in Clay Layer to Examine the Effect of Loading on Settlements and Skin Friction Distribution

Skin friction is a shear stress distributes along pile’s shaft as a reason of the movement between pile and adjacent soil. Applying loads on the pile head lead the pile to move downward and the adjacent soil to move upward resisting this movement, and a positive skin friction distribution will occur. On the other hand, applying a surcharge load on the surface next to the pile will cause extra settlements in the soil layers which may be larger than the pile settlements, and a negative skin friction (NSF) will be distributed along the pile’s shaft. Load combination on both; pile and the adjacent soil, is a common reason of NSF phenomenon. To study the loading effect widely, a parametric study was carried out in this paper for different cases including pile and surcharge loading. This parametric study was held by a numerical simulation using elastic-plastic soil model defined by Matsui-Abe and the elastic-viscoplastic soil model defined by Sekiguchi-Ohta model to study the case of a single pile driven in a loaded soft clay layer. The model was first validated by comparing the results obtained from the primary consolidation with field test measurements. The comparison between two soil constitutive models was important to examine the effect of loading in different cases of soil behavior. Viscosity effect on NSF distribution was studied and shown in the graphs. As NSF may lead to pile’s material fracture and structural failure, the aim of this paper is to examine the effect of loading on NSF, and clarify the viscosity behavior during primary consolidation stage. Viscous effect, surcharging and pile load combination have played a major rule in changing the skin friction distribution.