Pile design with consideration of down drag

Abstract

Pile design must be considered in three separate aspects: structural strength, displacement, and geotechnical capacity (bearing capacity). In the conventional design concept, the design bearing capacity of a pile does not take into account the negative friction, usually assumed to be about 30–40% of its ultimate capacity. The large safety factor in estimating the pile capacity is quite controversial. Many design methods have been proposed recently that take into account the negative friction effect. The approach is the calculation of: neutral plane, structural strength, soil settlement, pile displacement and, geotechnical capacity of pile. Meanwhile, the friction capacity at pile – soil interface estimated by the analytical formulas is obviously inaccurate and it is difficult to understand how the frictions are mobilized. This study proposes a simplified method for pile design that can overcome the mentioned difficulties. The results of this study show that this method may be applied to design practices.