President of Gaiatech specialised in geotechnical engineering for in situ tests, site survey, stability of earth works ( dikes and dams) under hydraulic conditions, compaction of soils...
European Journal of Environmental and Civil Engineering, Jun 1, 2012
In the first paper, part 1, we presented the elasto-plastic theory for the expansion of the press... more In the first paper, part 1, we presented the elasto-plastic theory for the expansion of the pressuremeter in granular soil. This theory allows determination of the behaviour of the granular soil around the pressuremeter with only four mechanical parameters. It is compared with previous theory on the dataset of the pressuremeter test on Ticino sand. In the second paper, part 2, we present the numerical analysis of the theoretical conventional limit pressure compared with the result of the Mohr–Coulomb non-standard model used by the Plaxis finite element program. The theoretical evolution of the conventional limit pressure as a function of the variation of each parameter shows a correct agreement with the numerical results. Conclusions are drawn on the influence of these parameters on the pressuremeter results.Dans un premier article, partie 1, nous présentons la théorie élasto-plastique de l’expansion de la sonde dans le sol granulaire. Cette théorie permet de déterminer le comportement du sol granulaire autour du pressiomètre avec seulement quatre paramètres mécaniques. Nous comparons ensuite ses résultats à ceux de théories plus anciennes pour l’étude des essais pressiométriques réalisés dans le sable de Ticino. Dans un second article, partie II, nous réalisons l’étude analytique de l’évolution de la pression limite donnée par cette théorie et nous la comparons à la valeur numérique trouvée avec le logiciel Plaxis L’évolution de la pression limite en fonction de la variation de chacun de ses paramètres montre un accord raisonnable avec les résultats numériques de Plaxis. Nous concluons sur l’importance relative de ces paramètres sur la pression limite.
L'AUTEUR PRESENTE UNE LOI DE COMPORTEMENT RHEOLOGIQUE A 5 PARAMETRES EN PARTANT DES TRAVAUX D... more L'AUTEUR PRESENTE UNE LOI DE COMPORTEMENT RHEOLOGIQUE A 5 PARAMETRES EN PARTANT DES TRAVAUX DE FRYMAN, ZEITLEN ET ALPAN QUI ONT EXPRIME LA VALEUR DE L'ENERGIE DE DEFORMATION AU CISAILLEMENT DU MILIEU PULVERULENT. CETTE LOI EST CARACTERISEE PAR UN COMPORTEMENT ELASTIQUE, PUIS UNE PHASE D'ECROUISSAGE DURCISSANT DONNANT UNE AUGMENTATION DE VOLUME DU SOL, ENFIN UN PALIER DE PLASTICITE PARFAITE CORRESPONDANT A LA RUPTURE. L'AUTEUR PRESENTE UNE EXTENSION DE CETTE LOI AU CAS DE L'ARGILE SURCONSOLIDEE ET DRAINEE EN SYMETRIE DE REVOLUTION. IL UTILISE DES ESSAIS PRATIQUES ANTERIEUREMENT POUR VERIFIER LES HYPOTHESES RETENUES ET COMPARER LES RESULTATS DU CALCUL AVEC L'EXPERIENCE TRIAXIALE.
The definition of the law linking the stresses and deformations of the soil enables the behaviour... more The definition of the law linking the stresses and deformations of the soil enables the behaviour of complex structures to be predicted with a computer. The Frydman Formula expressing the variation in soil deformation energy is used in the test to deduce the direction and length of the plastic deformation. The formulae obtained are directly applicable to the method of initial stresses by using the finite element method. A study is also conducted of the direction of plastic deformation to failure point. The calculations made during several series of triaxial tests on various materials (so as to vary the 4 parameters used) show a good agreement between theoretical and experimental results, thus making it possible to state the validity of the proposed law. dynamic bending may be deduced from that of total static bending, calculated from the load/deflection curve. (5) for the case of failure produced by yield of the reinforcement before degeneration of the concrete, the use of fibre reinforced concrete reduces the energy needed for bending failure. Conclusions are drawn relating to the design of beams subject to impact.
European Journal of Environmental and Civil Engineering, Jun 1, 2012
In this first paper, part I, we present the elasto-plastic theory for expansion of pressuremeters... more In this first paper, part I, we present the elasto-plastic theory for expansion of pressuremeters in granular soil. This theory allows determination of the behaviour of the granular soil around the pressuremeter with only four mechanical parameters. It is compared with previous theory on the dataset of the pressuremeter test on Ticino sand. In the second paper, part II, we
This study is related to the finite element computation of the tunnel face of the Lyon subway, wh... more This study is related to the finite element computation of the tunnel face of the Lyon subway, which was driven with a slurry pressure shield. The theoretical model of soil behaviour uses only 5 constant parameters which have a physical significance. It allows dilatancy along shearing process. The 3-dimensional computation shows the relation between the slurry pressure at the tunnel face, its displacements, the plastic areas, and the settlement in the open. The field measurements are conducted by inclinometer, tassometer, and by topography. The results are compared to the finite element ones. The amplitudes of the measured displacements compare well with those obtained by calculation. However the direction and distribution of these displacements cannot be modelled accurately by the method used. This emphasizes the major role played by shield-ground interaction, which isn't taken into account in the model. The face "characteristic curve" determined by this method can assess the horizontal stress level which should be applied to the face during excavation. (TRRL)
The calculations of flexible retaining walls based on the Winkler assumption can be criticized in... more The calculations of flexible retaining walls based on the Winkler assumption can be criticized in theory, but are increasingly used. This paper compares these calculations with a series of model tests, highlighting the possibilities and limitations of the method. The program used is based on the assumption of the modulus of subgrade reaction and limited values of active and passive earth pressure, while taking the soil hysteresis into account. Comparisons with conventional calculations and the finite element method are also presented. For the covering abstract of the conference see IRRD 287689. (TRRL)
LA COMPARAISON DES RESULTATS D'EXPERIMENTATION EN VRAIE GRANDEUR, DANS LES ALLUVIONS DU RHONE... more LA COMPARAISON DES RESULTATS D'EXPERIMENTATION EN VRAIE GRANDEUR, DANS LES ALLUVIONS DU RHONE, DE RIDEAUX DE PALPLANCHES OU EN PAROI PREFABRIQUEES AVEC DES CALCULS EFFECTUES PAR LA METHODE DU COEFFICIENT DE REACTION A FAIT APPARAITRE LES LIMITES DE CETTE HYPOTHESE. ON NOTE EN PARTICULIER QU'UNE BONNE CONCORDANCE ENTRE CALCULS ET MESURES NE S'OBTIENT QU'EN ATTRIBUANT AU RIDEAU UNE RAIDEUR FICTIVE (EI) NETTEMENT SUPERIEUR A LA VALEUR REELLE. DANS LES MEMES CONDITIONS, UN CALCUL EFFECTUE PAR LA METHODE DES ELEMENTS FINIS (PROGRAMME ROSALIE DU L.C.P.C.) UTILISANT UNE LOI DE COMPORTEMENT DU SOL ELASTOPLASTIQUE AVEC ECROUISSAGE DURCISSANT, DEVELOPPEE PAR MONNET, CONDUIT A UNE MEILLEURE CONCORDANCE CALCUL-EXPERIENCE : IL N'EST PAS NECESSAIRE D'ATTRIBUER ICI, AU SOL OU A LA PAROI, DES CARACTERISTIQUES "CORRIGEES" A L'AIDE DE LA COMPARAISON CALCUL-EXPERIENCE. L'ANALYSE DE CES RESULTATS MONTRE QUE LA DISCORDANCE ENTRE LES CALCULS AU "COEFFICIENT DE REACTION" ET LES MESURES EST DUE EN GRANDE PARTIE A LA NON PRISE EN COMPTE DES CONTRAINTES TANGENTIELLES AU CONTACT SOL-RIDEAU. LE CALCUL PAR LA M.E.F. MONTRE EN EFFET QUE CES CONTRAINTES REDUISENT LA COURBURE DE LA PAROI ET EXPLIQUENT AINSI SA PLUS GRANDE RAIDEUR APPARENTE. (A). (VOIR FICHE GENERALE DIRR 121853).
This paper presents the experimental and numerical analysis undertaken during the construction of... more This paper presents the experimental and numerical analysis undertaken during the construction of the Lyon subway tunnel through non cohesive sand gravel alluvium. The geology of the instrumented section of the tunnel and the physical and mechanical characteristics of the ground are described. Details of the instruments installed in the instrumented section of the tunnel are also provided. Instrumentation included: inclinometers, multiple anchor point extensometers, and pore pressure cells. A topographical study was also undertaken. The objective was to measure horizontal and vertical displacement of the overburden crossed by the shield tunnelling apparatus and the excess pore water pressure ahead of the tunnel face. Details of the measurements taken are provided and compared with those obtained by limit equilibrium, continum mechanic and finite element analyses. The laboratory and in situ test results and the 3 dimensional finite element analyses validated those obtained by 3 dimensional limiting equilibrium analysis. This analysis emphasises the influence of the pressure gradient at the tunnel face in sandy gravel soil and provides a safety factor. For the abstract of part 1 of this paper see IRRD 824083 and for the covering abstract of the conference see IRRD 824029.
This paper presents the experimental and numerical analysis undertaken during the construction of... more This paper presents the experimental and numerical analysis undertaken during the construction of the Lyon subway tunnel through non cohesive sand gravel alluvium. The geology of the instrumented section of the tunnel and the physical and mechanical characteristics of the ground are described. Details of the instruments installed in the instrumented section of the tunnel are also provided. Instrumentation included: inclinometers, multiple anchor point extensometers, and pore pressure cells. A topographical study was also undertaken. The objective was to measure horizontal and vertical displacement of the overburden crossed by the shield tunnelling apparatus and the excess pore water pressure ahead of the tunnel face. Details of the measurements taken are provided and compared with those obtained by limit equilibrium, continum mechanic and finite element analyses. The laboratory and in situ test results and the 3 dimensional finite element analyses validated those obtained by 3 dimensional limiting equilibrium analysis. This analysis emphasises the influence of the pressure gradient at the tunnel face in sandy gravel soil and provides a safety factor. For the abstract of part 1 of this paper see IRRD 824083 and for the covering abstract of the conference see IRRD 824029.
This theoretical model concerns sand behaviour when true triaxial shearing, and compressibility o... more This theoretical model concerns sand behaviour when true triaxial shearing, and compressibility occur. The main interest is the low number of parameters which always have a physical meaning. This model uses only 8 constant parameters for over-consolidated soil, and 6 for normally consolidated soil. The behaviour of the sand is assumed to be elastic in an area limited by an elliptical cap; beyond this cap, "standard" plasticity occurs in the compressible area, and "non-standard" plasticity in the dilatancy area. Theoretical results from the conventional triaxial test with a constant stress ratio are compared with the experimental results. (TRRL)
The Crozet bridge is located on the Grenoble-Col du Fau motorway, in the Grenoble- Sisteron intin... more The Crozet bridge is located on the Grenoble-Col du Fau motorway, in the Grenoble- Sisteron intinerary, fifteen kilometres south of Grenoble, Frace. It crosses a 350 m wide valley and the RN75 national road. The adaptation of the bridge to the lanscape has involved an arch design with three bays (direction of Grenoble-Sisteron) and one bay (direction of Sisteron-Grenoble). The
LE MODELE THEORIQUE QUI EST PRESENTE S'INTERESSE AU COMPORTEMENT DU SABLE PENDANT UN ESSAI DE... more LE MODELE THEORIQUE QUI EST PRESENTE S'INTERESSE AU COMPORTEMENT DU SABLE PENDANT UN ESSAI DE CISAILLEMENT TRIAXIAL VRAI. L'INTERET PRINCIPAL DE CETTE FORMULATION RESIDE DANS LE NOMBRE LIMITE DE PARAMETRES QUI SE RAMENENT TOUJOURS A UNE SIGNIFICATION PHYSIQUE. LE SOL EST SUPPOSE OBEIR A UN COMPORTEMENT ELASTIQUE, EN ECROUISSAGE DURCISSANT ET A UNE PLASTICITE PARFAITE "NON STANDARD". ON VERIFIE QUE L'ENERGIE DE DEFORMATION SUPPOSEE CORRESPOND A L'ENERGIE REELLEMENT DISSIPEE PENDANT L'ECROUISSAGE. ON FAIT EGALEMENT UN PARALLELE ENTRE CETTE THEORIE DES MILIEUX CONTINUS ET UNE THEORIE DE MILIEU DISCRET. ENFIN UNE COMPARAISON EST MENEE ENTRE LES RESULTATS THEORIQUES CALCULES POUR DIFFERENTS CHEMINS DE CONTRAINTE ET LES RESULTATS EXPERIMENTAUX CORRESPONDANTS. (A).
L'erosion interne est le resultat de l'arrachement des particules d'un sol sous l'... more L'erosion interne est le resultat de l'arrachement des particules d'un sol sous l'action d'un ecoulement hydraulique. Ce phenomene est a l'origine des ruptures hydrauliques des barrages et des digues. Sur le plan mondial, 46% des desordres observes, sur les ouvrages en terre, ont pour origine l'erosion interne. En France, 70 cas critiques ont deja ete detectes. Malheureusement, a cause du phenomene d'erosion lui-meme, la prevision du risque reste delicate et les autorites ont du mal a mettre en place des plans d'urgence. Compte tenu du risque potentiel, la comprehension des phenomenes a l'origine de l'erosion interne apparait comme un enjeu scientifique majeur. L'objectif du travail de these est de mettre au point une methode de diagnostic de l'erosion interne dans les digues et autres ouvrages en terre. Nous cherchons a etablir un protocole qui nous guidera sur les essais a faire et qui nous aidera a interpreter les resultats. Cette methode permettra d'expertiser les risques d'erosion interne. (i) Dans un premier temps, les principaux resultats des reconnaissances geomecaniques permettent d'identifier des couches geotechniques de sol de caracteristiques homogenes dans lesquelles sont realises les essais pressiometriques. L'analyse cluster des resultats des essais pressiometriques permet de determiner le type, la nature de sol, ainsi que les caracteristiques geotechniques moyennes. (ii) Les resultats obtenus servent ensuite a determiner si le sol est instable et quel est son seuil de sensibilite a l'aide du logiciel expert. Ce logiciel permet de calculer les criteres d'erosion interne et de qualifier la sensibilite du sol a l'erosion en determinant son seuil erosif. (iii) Un nouveau dispositif experimental appele l'Essai d'Erosion Transverse (Cross Erosion Test - CET) permet de caracteriser experimentalement le sol par rapport au risque d'erosion interne. Cet essai consiste a injecter de l'eau dans un forage, puis a pomper cette eau dans un forage parallele au premier. L'eau extraite est chargee en particules produites par l'erosion interne du sol. L'erosion est estimee en se basant sur la mesure de l'evolution de la masse des particules recueillies au cours du temps. Les resultats montrent que cette experience permet de caracteriser l'erosion interne dans un sol specifique. L'avantage de cette technique c'est qu'elle est transposable in situ et qu'elle peut etre utilisee pour predire le risque de suffusion dans les barrages et les digues. (iv) La validation de l'experience est faite par un modele numerique 3D realise avec le logiciel Comsol Multiphysics 4.3b. Ce modele permet de montrer que sous les conditions de permeabilite observees, le gradient hydraulique se concentre autour des points d'injection et de pompage. Une modelisation de base en 2D est developpee. Cette premiere approche permet de decrire le phenomene d'erosion et le transport des particules fines dans le milieu poreux du sol.
European Journal of Environmental and Civil Engineering, Jun 1, 2012
In the first paper, part 1, we presented the elasto-plastic theory for the expansion of the press... more In the first paper, part 1, we presented the elasto-plastic theory for the expansion of the pressuremeter in granular soil. This theory allows determination of the behaviour of the granular soil around the pressuremeter with only four mechanical parameters. It is compared with previous theory on the dataset of the pressuremeter test on Ticino sand. In the second paper, part 2, we present the numerical analysis of the theoretical conventional limit pressure compared with the result of the Mohr–Coulomb non-standard model used by the Plaxis finite element program. The theoretical evolution of the conventional limit pressure as a function of the variation of each parameter shows a correct agreement with the numerical results. Conclusions are drawn on the influence of these parameters on the pressuremeter results.Dans un premier article, partie 1, nous présentons la théorie élasto-plastique de l’expansion de la sonde dans le sol granulaire. Cette théorie permet de déterminer le comportement du sol granulaire autour du pressiomètre avec seulement quatre paramètres mécaniques. Nous comparons ensuite ses résultats à ceux de théories plus anciennes pour l’étude des essais pressiométriques réalisés dans le sable de Ticino. Dans un second article, partie II, nous réalisons l’étude analytique de l’évolution de la pression limite donnée par cette théorie et nous la comparons à la valeur numérique trouvée avec le logiciel Plaxis L’évolution de la pression limite en fonction de la variation de chacun de ses paramètres montre un accord raisonnable avec les résultats numériques de Plaxis. Nous concluons sur l’importance relative de ces paramètres sur la pression limite.
L'AUTEUR PRESENTE UNE LOI DE COMPORTEMENT RHEOLOGIQUE A 5 PARAMETRES EN PARTANT DES TRAVAUX D... more L'AUTEUR PRESENTE UNE LOI DE COMPORTEMENT RHEOLOGIQUE A 5 PARAMETRES EN PARTANT DES TRAVAUX DE FRYMAN, ZEITLEN ET ALPAN QUI ONT EXPRIME LA VALEUR DE L'ENERGIE DE DEFORMATION AU CISAILLEMENT DU MILIEU PULVERULENT. CETTE LOI EST CARACTERISEE PAR UN COMPORTEMENT ELASTIQUE, PUIS UNE PHASE D'ECROUISSAGE DURCISSANT DONNANT UNE AUGMENTATION DE VOLUME DU SOL, ENFIN UN PALIER DE PLASTICITE PARFAITE CORRESPONDANT A LA RUPTURE. L'AUTEUR PRESENTE UNE EXTENSION DE CETTE LOI AU CAS DE L'ARGILE SURCONSOLIDEE ET DRAINEE EN SYMETRIE DE REVOLUTION. IL UTILISE DES ESSAIS PRATIQUES ANTERIEUREMENT POUR VERIFIER LES HYPOTHESES RETENUES ET COMPARER LES RESULTATS DU CALCUL AVEC L'EXPERIENCE TRIAXIALE.
The definition of the law linking the stresses and deformations of the soil enables the behaviour... more The definition of the law linking the stresses and deformations of the soil enables the behaviour of complex structures to be predicted with a computer. The Frydman Formula expressing the variation in soil deformation energy is used in the test to deduce the direction and length of the plastic deformation. The formulae obtained are directly applicable to the method of initial stresses by using the finite element method. A study is also conducted of the direction of plastic deformation to failure point. The calculations made during several series of triaxial tests on various materials (so as to vary the 4 parameters used) show a good agreement between theoretical and experimental results, thus making it possible to state the validity of the proposed law. dynamic bending may be deduced from that of total static bending, calculated from the load/deflection curve. (5) for the case of failure produced by yield of the reinforcement before degeneration of the concrete, the use of fibre reinforced concrete reduces the energy needed for bending failure. Conclusions are drawn relating to the design of beams subject to impact.
European Journal of Environmental and Civil Engineering, Jun 1, 2012
In this first paper, part I, we present the elasto-plastic theory for expansion of pressuremeters... more In this first paper, part I, we present the elasto-plastic theory for expansion of pressuremeters in granular soil. This theory allows determination of the behaviour of the granular soil around the pressuremeter with only four mechanical parameters. It is compared with previous theory on the dataset of the pressuremeter test on Ticino sand. In the second paper, part II, we
This study is related to the finite element computation of the tunnel face of the Lyon subway, wh... more This study is related to the finite element computation of the tunnel face of the Lyon subway, which was driven with a slurry pressure shield. The theoretical model of soil behaviour uses only 5 constant parameters which have a physical significance. It allows dilatancy along shearing process. The 3-dimensional computation shows the relation between the slurry pressure at the tunnel face, its displacements, the plastic areas, and the settlement in the open. The field measurements are conducted by inclinometer, tassometer, and by topography. The results are compared to the finite element ones. The amplitudes of the measured displacements compare well with those obtained by calculation. However the direction and distribution of these displacements cannot be modelled accurately by the method used. This emphasizes the major role played by shield-ground interaction, which isn't taken into account in the model. The face "characteristic curve" determined by this method can assess the horizontal stress level which should be applied to the face during excavation. (TRRL)
The calculations of flexible retaining walls based on the Winkler assumption can be criticized in... more The calculations of flexible retaining walls based on the Winkler assumption can be criticized in theory, but are increasingly used. This paper compares these calculations with a series of model tests, highlighting the possibilities and limitations of the method. The program used is based on the assumption of the modulus of subgrade reaction and limited values of active and passive earth pressure, while taking the soil hysteresis into account. Comparisons with conventional calculations and the finite element method are also presented. For the covering abstract of the conference see IRRD 287689. (TRRL)
LA COMPARAISON DES RESULTATS D'EXPERIMENTATION EN VRAIE GRANDEUR, DANS LES ALLUVIONS DU RHONE... more LA COMPARAISON DES RESULTATS D'EXPERIMENTATION EN VRAIE GRANDEUR, DANS LES ALLUVIONS DU RHONE, DE RIDEAUX DE PALPLANCHES OU EN PAROI PREFABRIQUEES AVEC DES CALCULS EFFECTUES PAR LA METHODE DU COEFFICIENT DE REACTION A FAIT APPARAITRE LES LIMITES DE CETTE HYPOTHESE. ON NOTE EN PARTICULIER QU'UNE BONNE CONCORDANCE ENTRE CALCULS ET MESURES NE S'OBTIENT QU'EN ATTRIBUANT AU RIDEAU UNE RAIDEUR FICTIVE (EI) NETTEMENT SUPERIEUR A LA VALEUR REELLE. DANS LES MEMES CONDITIONS, UN CALCUL EFFECTUE PAR LA METHODE DES ELEMENTS FINIS (PROGRAMME ROSALIE DU L.C.P.C.) UTILISANT UNE LOI DE COMPORTEMENT DU SOL ELASTOPLASTIQUE AVEC ECROUISSAGE DURCISSANT, DEVELOPPEE PAR MONNET, CONDUIT A UNE MEILLEURE CONCORDANCE CALCUL-EXPERIENCE : IL N'EST PAS NECESSAIRE D'ATTRIBUER ICI, AU SOL OU A LA PAROI, DES CARACTERISTIQUES "CORRIGEES" A L'AIDE DE LA COMPARAISON CALCUL-EXPERIENCE. L'ANALYSE DE CES RESULTATS MONTRE QUE LA DISCORDANCE ENTRE LES CALCULS AU "COEFFICIENT DE REACTION" ET LES MESURES EST DUE EN GRANDE PARTIE A LA NON PRISE EN COMPTE DES CONTRAINTES TANGENTIELLES AU CONTACT SOL-RIDEAU. LE CALCUL PAR LA M.E.F. MONTRE EN EFFET QUE CES CONTRAINTES REDUISENT LA COURBURE DE LA PAROI ET EXPLIQUENT AINSI SA PLUS GRANDE RAIDEUR APPARENTE. (A). (VOIR FICHE GENERALE DIRR 121853).
This paper presents the experimental and numerical analysis undertaken during the construction of... more This paper presents the experimental and numerical analysis undertaken during the construction of the Lyon subway tunnel through non cohesive sand gravel alluvium. The geology of the instrumented section of the tunnel and the physical and mechanical characteristics of the ground are described. Details of the instruments installed in the instrumented section of the tunnel are also provided. Instrumentation included: inclinometers, multiple anchor point extensometers, and pore pressure cells. A topographical study was also undertaken. The objective was to measure horizontal and vertical displacement of the overburden crossed by the shield tunnelling apparatus and the excess pore water pressure ahead of the tunnel face. Details of the measurements taken are provided and compared with those obtained by limit equilibrium, continum mechanic and finite element analyses. The laboratory and in situ test results and the 3 dimensional finite element analyses validated those obtained by 3 dimensional limiting equilibrium analysis. This analysis emphasises the influence of the pressure gradient at the tunnel face in sandy gravel soil and provides a safety factor. For the abstract of part 1 of this paper see IRRD 824083 and for the covering abstract of the conference see IRRD 824029.
This paper presents the experimental and numerical analysis undertaken during the construction of... more This paper presents the experimental and numerical analysis undertaken during the construction of the Lyon subway tunnel through non cohesive sand gravel alluvium. The geology of the instrumented section of the tunnel and the physical and mechanical characteristics of the ground are described. Details of the instruments installed in the instrumented section of the tunnel are also provided. Instrumentation included: inclinometers, multiple anchor point extensometers, and pore pressure cells. A topographical study was also undertaken. The objective was to measure horizontal and vertical displacement of the overburden crossed by the shield tunnelling apparatus and the excess pore water pressure ahead of the tunnel face. Details of the measurements taken are provided and compared with those obtained by limit equilibrium, continum mechanic and finite element analyses. The laboratory and in situ test results and the 3 dimensional finite element analyses validated those obtained by 3 dimensional limiting equilibrium analysis. This analysis emphasises the influence of the pressure gradient at the tunnel face in sandy gravel soil and provides a safety factor. For the abstract of part 1 of this paper see IRRD 824083 and for the covering abstract of the conference see IRRD 824029.
This theoretical model concerns sand behaviour when true triaxial shearing, and compressibility o... more This theoretical model concerns sand behaviour when true triaxial shearing, and compressibility occur. The main interest is the low number of parameters which always have a physical meaning. This model uses only 8 constant parameters for over-consolidated soil, and 6 for normally consolidated soil. The behaviour of the sand is assumed to be elastic in an area limited by an elliptical cap; beyond this cap, "standard" plasticity occurs in the compressible area, and "non-standard" plasticity in the dilatancy area. Theoretical results from the conventional triaxial test with a constant stress ratio are compared with the experimental results. (TRRL)
The Crozet bridge is located on the Grenoble-Col du Fau motorway, in the Grenoble- Sisteron intin... more The Crozet bridge is located on the Grenoble-Col du Fau motorway, in the Grenoble- Sisteron intinerary, fifteen kilometres south of Grenoble, Frace. It crosses a 350 m wide valley and the RN75 national road. The adaptation of the bridge to the lanscape has involved an arch design with three bays (direction of Grenoble-Sisteron) and one bay (direction of Sisteron-Grenoble). The
LE MODELE THEORIQUE QUI EST PRESENTE S'INTERESSE AU COMPORTEMENT DU SABLE PENDANT UN ESSAI DE... more LE MODELE THEORIQUE QUI EST PRESENTE S'INTERESSE AU COMPORTEMENT DU SABLE PENDANT UN ESSAI DE CISAILLEMENT TRIAXIAL VRAI. L'INTERET PRINCIPAL DE CETTE FORMULATION RESIDE DANS LE NOMBRE LIMITE DE PARAMETRES QUI SE RAMENENT TOUJOURS A UNE SIGNIFICATION PHYSIQUE. LE SOL EST SUPPOSE OBEIR A UN COMPORTEMENT ELASTIQUE, EN ECROUISSAGE DURCISSANT ET A UNE PLASTICITE PARFAITE "NON STANDARD". ON VERIFIE QUE L'ENERGIE DE DEFORMATION SUPPOSEE CORRESPOND A L'ENERGIE REELLEMENT DISSIPEE PENDANT L'ECROUISSAGE. ON FAIT EGALEMENT UN PARALLELE ENTRE CETTE THEORIE DES MILIEUX CONTINUS ET UNE THEORIE DE MILIEU DISCRET. ENFIN UNE COMPARAISON EST MENEE ENTRE LES RESULTATS THEORIQUES CALCULES POUR DIFFERENTS CHEMINS DE CONTRAINTE ET LES RESULTATS EXPERIMENTAUX CORRESPONDANTS. (A).
L'erosion interne est le resultat de l'arrachement des particules d'un sol sous l'... more L'erosion interne est le resultat de l'arrachement des particules d'un sol sous l'action d'un ecoulement hydraulique. Ce phenomene est a l'origine des ruptures hydrauliques des barrages et des digues. Sur le plan mondial, 46% des desordres observes, sur les ouvrages en terre, ont pour origine l'erosion interne. En France, 70 cas critiques ont deja ete detectes. Malheureusement, a cause du phenomene d'erosion lui-meme, la prevision du risque reste delicate et les autorites ont du mal a mettre en place des plans d'urgence. Compte tenu du risque potentiel, la comprehension des phenomenes a l'origine de l'erosion interne apparait comme un enjeu scientifique majeur. L'objectif du travail de these est de mettre au point une methode de diagnostic de l'erosion interne dans les digues et autres ouvrages en terre. Nous cherchons a etablir un protocole qui nous guidera sur les essais a faire et qui nous aidera a interpreter les resultats. Cette methode permettra d'expertiser les risques d'erosion interne. (i) Dans un premier temps, les principaux resultats des reconnaissances geomecaniques permettent d'identifier des couches geotechniques de sol de caracteristiques homogenes dans lesquelles sont realises les essais pressiometriques. L'analyse cluster des resultats des essais pressiometriques permet de determiner le type, la nature de sol, ainsi que les caracteristiques geotechniques moyennes. (ii) Les resultats obtenus servent ensuite a determiner si le sol est instable et quel est son seuil de sensibilite a l'aide du logiciel expert. Ce logiciel permet de calculer les criteres d'erosion interne et de qualifier la sensibilite du sol a l'erosion en determinant son seuil erosif. (iii) Un nouveau dispositif experimental appele l'Essai d'Erosion Transverse (Cross Erosion Test - CET) permet de caracteriser experimentalement le sol par rapport au risque d'erosion interne. Cet essai consiste a injecter de l'eau dans un forage, puis a pomper cette eau dans un forage parallele au premier. L'eau extraite est chargee en particules produites par l'erosion interne du sol. L'erosion est estimee en se basant sur la mesure de l'evolution de la masse des particules recueillies au cours du temps. Les resultats montrent que cette experience permet de caracteriser l'erosion interne dans un sol specifique. L'avantage de cette technique c'est qu'elle est transposable in situ et qu'elle peut etre utilisee pour predire le risque de suffusion dans les barrages et les digues. (iv) La validation de l'experience est faite par un modele numerique 3D realise avec le logiciel Comsol Multiphysics 4.3b. Ce modele permet de montrer que sous les conditions de permeabilite observees, le gradient hydraulique se concentre autour des points d'injection et de pompage. Une modelisation de base en 2D est developpee. Cette premiere approche permet de decrire le phenomene d'erosion et le transport des particules fines dans le milieu poreux du sol.
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Papers by Jacques Monnet