Analysis of behavior of sand surrounding pile tips

A finite element approach is presented to predict the behaviour of dense sand surrounding the pile tip in a fairly large stress range, from low stress levels to very high ones, where particle-breakage occurs. The approach is based on a constitutive model for sand, which is characterized by critical state type yield surfaces and by a non-linear Mohr-Coulomb failure criterion, the latter being defined on the basis of constant volume shear strength and of dilatancy. In addition, the concept of constant relative breakage surfaces, which represent families of curves characterized by constant amounts of particle-crushing, is introduced. It is shown that the model, applied to the analysis of the behaviour of the tip of non-displacement piles in sand, can be utilized to visualize and to predict the distribution of strength, dilatancy and grain-breakage in the soil surrounding the pile base.