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Seyssins, France

Monnet J.,Joseph Fourier University | Boutonnier L.,EGIS Geotechnique
Archives of Civil and Mechanical Engineering | Year: 2012

A theoretical model of unsaturated soil is presented. It takes into account the three main components of the soil: the air; the water; and the soil particles. It uses the principle of effective stress on four different domains: unsaturated with the air in continuous phase (Domain D1), unsaturated with the air occluded in contact with the particles of soil (Domain D2), unsaturated with air bubbles (Domain D3), and saturated with the air dissolved into the water (Domain D4). The model is validated on isotropic compression tests and on oedometer tests. The determination of the parameters of the unsaturated model is explained and the mean values of the parameters are presented. © 2012 Politechnika WrocŁawska.

Villard P.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Huckert A.,EGIS Geotechnique | Briancon L.,INSA Lyon
Geotextiles and Geomembranes | Year: 2016

A numerical model was used to investigate the mechanical behaviour of granular embankments reinforced by geosynthetics in areas prone to subsidence and to overcome the shortcomings of the current design methods. The ability of the numerical model to consider the load transfer mechanisms and the deflection of the geosynthetic was established by comparison with experimental data. By testing two numerical processes, it was demonstrated that the cavity opening modes have a great influence on the shape of the load distribution transmitted to the geosynthetic sheet above the cavity and on the expansion mechanisms of the soil. An approximate conical load distribution seems well adapted when considering a progressive cavity diameter opening process, whereas an inverted load distribution seems more suitable for a gradual settlement process. In both cases, the intensity of the load transfer mechanism can be approached by the Terzaghi's formulation using an appropriate value for the ratio between the horizontal and vertical stresses. Finally, recommendations based on the experimental and numerical results are proposed to promote a better design of such structures. © 2016 Elsevier Ltd.

Regazzoni P.-L.,EGIS Geotechnique | Marot D.,University of Nantes
Natural Hazards | Year: 2013

Interface erosion is one of the main phenomena in dams, dikes and their foundations which may increase their failure risk. In laboratories, the jet erosion test (JET) and the hole erosion test (HET) are commonly used for the evaluation of the sensibility of interface erosion of fine soils. The results are interpreted by two distinct methods that are valid for one test only. A new energy analysis of the tests is developed, relating the total eroded mass to the dissipated fluid energy, and a new erosion resistance index is proposed. Seven naturally occurring fine-grained soils, covering a large range of erodibility, are compacted with the Proctor protocol, and they are tested with the two devices. It was shown that by using the commonly used methods, the values of the erosion coefficient are systematically higher with the JET than with the HET and the HET critical shear stress is about fifty times higher than the JET critical shear stress. Thus, the relative soil classifications yielded by the two erodimeters are not exactly the same. Based on energy analysis, values of erosion resistance index are roughly the same for each tested soil with the two apparatuses and a single classification of soil erodibility is obtained. © 2013 Springer Science+Business Media Dordrecht.

Breugnot A.,EGIS Geotechnique | Breugnot A.,Grenoble Universites | Gotteland Ph.,Grenoble Universites | Villard P.,Grenoble Universites
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010

This paper investigates modelling of granular material submitted to high energy impact due to block impact. An original combined discrete - continuum method is proposed which permits to use discrete element method to model precisely the complex behaviour of granular material in the vicinity of the impacted zonewhile a continuum approach is used in farther areas. Coupled methods proposed are validated through simple static and dynamic tests and, finally used to simulate high energy impact of a cubic impactant on a gravel layer. © 2010 Taylor & Francis Group, London.

Huckert A.,EGIS Geotechnique | Reynaud S.,EGIS Geotechnique | Villard P.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

Rigid inclusions used to limit settlements of embankments over soils with low characteristics are more and more completed with a geogrid, placed at the base of the embankment. The design of this geogrid remains difficult, since load transfers within the embankment and the solicitation of these reinforcements remain not well known. Recent developments enabled to precise the reaction of the subsoil, but without taking into account the interaction between this subsoil and the rigid inclusions. Hence an alternative design methodology is proposed and its results are confronted to existing analytical methods and measurements. © The authors and ICE Publishing: All rights reserved, 2015.

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