Tensile and Compressive Shaft Capacity of Piles in Sand

Abstract

In most soil types, it is generally assumed that the shaft capacity of a pile is identical under both tensile and compressive loading. However, there is widespread experimental evidence that in sand the shaft capacity is significantly lower for tensile loading, or uplift, than for compressive loading. This paper describes the results of a parametric study that was conducted to explore the theoretical basis for such differences. It is shown that the primary cause of lower tensile capacity is due to a Poisson’s ratio effect, and that the ratio of tensile to compressive shaft capacity may be expressed as a function of the relative compressibility of the pile and the slenderness ratio. Design recommendations are proposed, and corroborated with results from high-quality field tests.