Negative skin friction on single piles in clay subjected to direct and indirect loading

A numerical model employing the finite element technique is developed to analyze the negative skin friction induced in single floating piles subjected to direct and indirect loading. The pile is embedded in saturated clay. The clay is subjected to surcharge pressure for generating indirect loading on the pile. The soil is assumed to behave as a linearly elastic perfectly plastic material with a yield function defined by the Mohr-Coulomb equation. The results of the numerical model compared well with the field data. A parametric study is presented to show the influence of various parameters on the location of neutral plane. It has been found that the level of direct loading introduced in terms of factor of safety has a major effect in locating the neutral plane. Based on the results of the present investigation, a design formula together with design charts are given for determining the allowable bearing capacity of coated and uncoated single piles.