VISCOSITY EFFECT ON SOIL SETTLEMENTS AND PILE SKIN FRICTION DISTRIBUTION DURING PRIMARY CONSOLIDATION

Abstract

Skin friction distribution occurs due to a relative movement between pile and adjacent soil. Varied factors affecting this movement get the soil to, occasionally, settle more than that of the pile. In this case, negative skin friction distributes along some part of the pile's shaft. Primary consolidation begins after applying surcharge load on ground surface next to pile’s head - where pressure will be carried by the pore water until the entire excess pore pressure dissipates and shear stressis mobilized. This paper presents a finite element parametric study to investigate the effect of viscosity on soil settlements and skin friction distribution along the pile during primary consolidation. Single pile in clay soil is modelled using FORTRAN in conjunction with two different soil constitutive models. On the one hand, numerical modeling has been carried out using the elasto-plastic soil behavior – as defined by Matsui-Abe soil constitutive model. On the other hand, the effect of viscosity has been modeled using the elasto-viscoplastic soil model as defined by Sekiguchi-Ohta model. A parametric study has been conducted in order to compare the results of the above two soil models to clarify the viscous impact. FORTRAN 2-D analytical model has been validated by comparing numerical results with two field tests measurements. Viscosity is clearly effective when a specific value of surcharge load is applied. Structural viscosity has increased the soil settlements compared to the other settlements that occurred by using elasto-plastic soil model – where part of the pile induced by negative skin friction becomes greater.