Steinar Nordal

On Shear-Volume Coupling in Deformation of Soils

Mathematical formalisms of shear-volume coupling for geomaterials, also known as stress-dilatancy relationships, are central components to a majority of constitutive models for soils. This paper investigates various stress-dilatancy formulations comparatively such that the consequence of adopting them in constitutive modeling can be easily understood.

A new elasto-plastic spring element for cyclic loading of piles using the p-y-curve concept

Modeling the response of large diameter piles subjected to lateral loading is most often done by means of p-y-curves in combination with Winkler beam models. Traditionally the p-y curves are formulated as non-linear (elastic) relations between the lateral movement y and the soil response pressure p in terms of monotonic loading (until failure) as e.g. prescribed byAPI (2000). However, the cyclic and dynamic performance is only to a limited degree accounted for. Here the elasto-plastic framework is applied allowing definition of unloading-reloading branches, hence enabling modeling of cyclic response. The present model can account for effects like pre-consolidation and creation of gaps between pile and soil at reversed loading. Results indicate that the model is able to capture hysteresis during loading with full cycles and model the accumulated displacement observed on piles subjected to “half cycles” as e.g. seen from centrifuge tests carried out. This article presents the theoretical formulations, discusses numerical implementation and finally presents simulations.