Thomas Benz

Site Monitoring and Numerical Modelling of a Trial Embankment's Behaviour on Venice Lagoon Soils

Mineralogical and mechanical characterization of Venice lagoon soils is required for design and construction of movable floodgates that aim to safeguard the city of Venice against recurrent floods. An instrumented circular test embankment was constructed in the lagoon area, enabling accurate measurement of relevant ground displacements. In situ stress-strain-time measurements were carried out in order to investigate the viscous behaviour of Venice lagoon soils during and after embankment loading. Site monitoring was kept up also during embankment removal so that information on soil behaviour in unloading is available, too. This paper illustrates key results from embankment monitoring and also focuses on modelling of creep behaviour. A recently developed anisotropic constitutive model was calibrated for Venice lagoon soils and is used in back analysis of the embankment construction and removal process. The constitutive parameters of the model were calibrated from in situ and laboratory tests.

Stress-Dependency of Intergranular Strain

Various experimental results show that small strain stiffness and its decay with shear strain depend on confining pressure amongst other factors. In this paper, a selection of experimental evidence is briefly discussed. The Intergranular Strain formulation by Niemunis & Herle (1997) for the hypoplastic theory is extended for the same effect and evaluated. Furthermore, application of the concept to elastoplastic models is discussed.

Back Analysis of Treporti Test Embankment with a Time Dependent Small Strain Stiffness Constitutive Model

This paper is concerned with back analysis of a trial embankment on soft soil. The analysis is conducted with and without consideration of small strain stiffness in the time dependent soft soil constitutive model. Whilst in loading during embankment construction small strain stiffness is found to be of minor importance, it is predominant in unloading. In unloading, the small strain enhanced model predicts deformations with considerably higher accuracy than its counterpart without small strain stiffness formulation. The time dependent small strain stiffness model is based on a recently proposed anisotropic creep framework and a strain space based small strain stiffness formulation.

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.