EGIS Geotechnique

Seyssins, France

EGIS Geotechnique

Seyssins, France

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Monnet J.,GAIATECH | Mahmutovic D.,EGIS Geotechnique | Boutonnier L.,EGIS Geotechnique
Proceedings of the 5th International Conference on Geotechnical and Geophysical Site Characterisation, ISC 2016 | Year: 2016

The pressuremeter standards allows only two corrections: on the dilatation of the equipment; on the membrane rigidity. It assumes that the pressure applied into the probe is equal to the reaction pressure of the soil at the borehole wall. It neglects the effect of the thickness of the membrane and its defor-mation shape. This paper takes into account the effect of thickness of the membrane and its balloon shaped deformation with new corrections applied on the pressuremeter measurements. A theoretical correction is proposed and check by the results of a finite element calculation which takes into account the presence of two type of membrane: one in free ends for probe G, one with embedded ends for slotted tube probe. With these corrections, the pressuremeter test can be used as a shearing test able to measure the shearing elastic and plas-tic characteristics of the soil. © 2016 Australian Geomechanics Society.

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.

Huckert A.,Egis Geotechnique | Garcin P.,Egis Geotechnique | Villard P.,Grenoble Institute of Technology | Briancon L.,French National Conservatory of Arts and Crafts | Auray G.,Texinov
10th International Conference on Geosynthetics, ICG 2014 | Year: 2014

After leading a full scale experiment where a circular sinkhole of rising diameter is progressively opened under a geosynthetic-reinforced embankment, the experimental results are compared to the result of discrete numerical simulations. This numerical model provides further information where experimental data lack, for instance the value of the mean vertical stress on the geosynthetic overlying the void, or the shape of the load distribution on the geosynthetic reinforcement. Thus new analytical developments taking into account the numerical non-uniform load distribution on the geosynthetic are suggested and validated by both experimental and numerical results.

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.

Huckert A.,Laboratoire 3SR | Villard P.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Briancon L.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Garcin P.,Egis Geotechnique
Design and Practice of Geosynthetic-Reinforced Soil Structures | Year: 2013

The design of geosynthetic-reinforced embankments overlying sinkholes remains problematic due to complex and combined mechanisms such as the load transfers within the embankment, the bending effect of the geosynthetic over the cavity or the frictional interactions between the soil and the geosynthetic. For a better understanding of such mechanisms, three full-scale experimentations were lead, and their results were compared to the results of the most recent analytical method. In the end, these comparisons enabled to underline some lacks in the analytical hypothesis, as the vertical load on the reinforcement due to arching effect in a granular layer or breaking mechanisms for a cohesive soil layer.

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.

Guerpillon Y.,Egis Geotechnique | Virollet M.,Egis Geotechnique
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

Substantial settlement occurred after construction of the Kingston-Portmore motorway. Monitoring and interpretation of these strains give reinforcement methods which can reduce the settlement rates to make them compatible with the safety of the carriage ways. © The authors and ICE Publishing: All rights reserved, 2015.

Huckert A.,EGIS Geotechnique | Briancon L.,INSA Lyon | Villard P.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Garcin P.,EGIS Geotechnique
Geotextiles and Geomembranes | Year: 2015

The techniques of soil reinforcement by geotextile are easy and economic solutions that limit the surface settlements of embankments prone to sinkholes. The design of such structures is based on understanding complex mechanisms, such as the tensile geosynthetic behavior under vertical loading, the frictional interaction between the soil and the reinforcement, the load transfer mechanisms and the arching effect in the soil embankment. Recently, significant progress has been made, allowing for improvement of the design methods by taking into account the frictional and sliding effects of the geosynthetic sheet in the anchorage areas and the local increase of the vertical stresses in the vicinity of the edges of the cavity. Nevertheless, the soil dilatancy, or the load transfer mechanisms in the embankment during the formation of the cavity or under static or cyclic loadings, remains unknown. Additionally, the reinforced, treated soil layer has not been specifically studied. To focus on the soil embankment behavior over a void, experimental studies were conducted as part of the FUI research project GéoInov.Sinkholes are experimentally simulated under granular embankments and treated soil layers, both reinforced by geotextiles. Each void is created by a device that allows the progressive formation of a circular cavity with an increasing diameter of 0.75, 1.25 and 2.2m. This enables reproduction of the formation of some natural sinkholes. After the void reaches a size of 2.2m wide, traffic loads are applied on the top surface of the embankment. Then, during both the formation of the cavity and the vehicle traffic loading, a dedicated instrumentation is used to measure the dilatancy and the soil movement, the load transfer, the deformation of the geotextile and the surface settlement. The experimental results are then analyzed and compared with existing analytical methods to improve the existing analytical methods. © 2015 Elsevier Ltd.

Huckert A.,Egis Geotechnique | Reynaud S.,Egis Geotechnique | Villard P.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Auray G.,Texinov la Tour du Pin
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.

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.

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