Heavy Vehicle Transport Technology (HVTT 10), 2013
... Une méthode de calcul de structures soumises à des chargements mobiles, Revue européenne des ... more ... Une méthode de calcul de structures soumises à des chargements mobiles, Revue européenne des éléments finis. 11(2-3-4): 247–261. • Ouakka, A. (1993). ... A New Approach to Inelastic Analysis of Structures, Martinus Nijhoff, Dordrecht/Boston/Lancaster.
Geometryofballastedrailwaystrackisamajorconcerninrailroadssafetyand efficiency. Settlement of railw... more Geometryofballastedrailwaystrackisamajorconcerninrailroadssafetyand efficiency. Settlement of railways ballast has been studied to help railway infrastructure managers to keep infrastructures in shape and to prevent accidents. In this paper, we present an innovative numerical approach to study railways ballast settlement. Commonly used models representing a moving load need huge computation time. On the other hand, assuming static cyclic loading representation leads to discrepancies. Indeed, it does not conceder particularities of moving load. With this new model we want to avoid the drawbacks of previously developed methods. We developed a steady state algorithm to compute plastic strain in geomaterials and to study behaviour of ballasted railways track with an Eulerian approach. This way we improved model efficiency by drastically reducing computation time while considering mobile load specificities.
Un critere general lisse et convexe est propose pour modeliser le comportement specifique des geo... more Un critere general lisse et convexe est propose pour modeliser le comportement specifique des geomateriaux, particulierement les roches. Ces caracteristiques sont definies par deux fonctions : l'equation du critere dans le plan meridien principal et le ratio d'extension. Elles sont integrees dans une equation garantissant le caractere regulier et convexe de la fonction de charge independamment des fonctions caracteristiques. Cette expression permet la constitution directe d'un modele a partir des essais triaxiaux, en extension et en compression, ainsi que le developpement des formes regularisees correspondant au critere de Coulomb et au critere de Hoek-Brown. Pour calculer numeriquement les deformations plastiques, on demontre l'equivalence entre le probleme numerique (projection sur le point le plus proche) et une configuration geometrique bornee, independante du probleme physique. On peut ainsi constituer des abaques numeriques qui, charges par un logiciel d'el...
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA... more In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA (known at the time as CETE de Lyon), following the fire of September 2008 in che Channel tunnel. Whereas chalk marl was unaffected by the fire even in the most damaged zone, several laboratory test were performed, during the shutdown of the north tunnel. At the request of Eurotunnel society, we determined that the rock behavior was characterized by an extreme sensitivity to water content: • Young Modulus and Uniaxial Compressive are function of water content , with the same power law. • Unless conserved in a fully saturated atmosphere, chalk marl of the Channel tunnel loses water at an important hourly rate and is totally dry in a few days. This experience was useful for the SAFE project: in the first major modification to the Tunnel infrastructure since it was built, 4 SAFE fire-fighting stations were built. They became operational at the end of 2011. Those stations permit now to contain a major fire. The results of rock mechanics tests performed on samples were conform to the observation made a few months before, in a zone characterized by a higher water content.
A general smooth and convex yield function had been proposed , able to model the particular behav... more A general smooth and convex yield function had been proposed , able to model the particular behavior of porous materials, particularly rock materials, that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane. These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. In this paper, further developments of the criterion are made to encompass to modelize the behavior of damaged, weathered or heavily fractured rocks. We identify the functions that allow to develop a smooth version of the generalized Hœk-Brown criterion. So it can be use do predict the behavior of rock masses, relying on identification on intact core sample, and taking into account observations made by geologist and field engineers through the Geological Streng...
While the Mohr-Coulomb criterion is widely used in geotechnics, the Drucker-Prager is common in f... more While the Mohr-Coulomb criterion is widely used in geotechnics, the Drucker-Prager is common in finite element software. Its circular shape is really a great advantage from a numerical point of view, even it is a drawback from a physical point of view. In contrast, the Matsuoka-Nakai criterion seems to best fit material behaviour, particularly with regard to true triaxial tests. Moreover its smooth shape is also closer to the Mohr-Coulomb shape than that of the Drucker-Prager. However, the circular shape of Drucker-Prager allows rapid and straightforward computations of plastic strain, due to the use of the radial return closed form. In contrast, the closest point projection method used to compute plastic strain for other criteria is more complex to implement and requires more computation time. Maiolino and Luong have shown that using the Drucker-Prager criterion as a substitution for a Mohr-Coulomb criterion induces great discrepancies of the friction angle. But in previous work, t...
Computing plastic strain is a crucial issue in finite element methods. This problem is also known... more Computing plastic strain is a crucial issue in finite element methods. This problem is also known as closest point projection. The radial return used for circular models reduces the computations to literal expressions. But in geomechanics, the deviatoric shape of yield functions is generally non circular, so that return mapping algorithm becomes cumbersome and time consuming. Works that will be presented rather focus on a geometric based methods. It will be demonstrated that the numerical problem of closest point projection of the trial stress on the yield surface is equivalent to a geometrical bounded problem. Whereas this property is intuitive, the tools ensuring a straightforward equivalence between the two problems were to be developed. We identify the geometric problem associated to the problem of the closest point projection in the deviatoric plane. The geometric problem is independent from the mechanical one, and can be solved with trigonometric and geometric laws. Those laws...
Cette thèse aborde à la fois des aspects comportementaux et numériques de la réponse mécanique du... more Cette thèse aborde à la fois des aspects comportementaux et numériques de la réponse mécanique du massif rocheux au creusement d'un tunnel. La comparaison de critères existants a mis l'accent sur quelques points clefs, comme la dépendance du critère à la contrainte moyenne et le ratio d'extension. Une fonction de charge, aisément identifiable à partir des essais, au caractère régulier et convexe, capable de tenir compte de la forme de l'enveloppe de Mohr du critère, ainsi que du ratio d'extension, a été proposée : on peut ainsi réaliser des formes régularisées des critères de Mohr-Coulomb et de Hœk-Brown. Le développement de ce nouveau critère a été complété par la proposition d'une méthode d'abaques numériques, accélérant grandement la résolution. Pour le critère proposé, le problème physique est équivalent à un problème purement géométrique, en coordonnées polaires dans le plan. On peut ainsi constituer des abaques numériques qui permettent d'obtenir...
A general smooth and convex yield function is proposed, able to model the particular behavior of ... more A general smooth and convex yield function is proposed, able to model the particular behavior of geomaterials, particularly rock materials that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane. These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. This expression is interesting, because it allows a straightforward development of a constitutive model based on triaxial tests, in extension and compression. It also allows the development of smooth criteria corresponding to the Mohr–Coulomb criterion and the Hoek–Brown criterion, the latter typical of rock mechanics.
Heavy Vehicle Transport Technology (HVTT 10), 2013
... Une méthode de calcul de structures soumises à des chargements mobiles, Revue européenne des ... more ... Une méthode de calcul de structures soumises à des chargements mobiles, Revue européenne des éléments finis. 11(2-3-4): 247–261. • Ouakka, A. (1993). ... A New Approach to Inelastic Analysis of Structures, Martinus Nijhoff, Dordrecht/Boston/Lancaster.
Geometryofballastedrailwaystrackisamajorconcerninrailroadssafetyand efficiency. Settlement of railw... more Geometryofballastedrailwaystrackisamajorconcerninrailroadssafetyand efficiency. Settlement of railways ballast has been studied to help railway infrastructure managers to keep infrastructures in shape and to prevent accidents. In this paper, we present an innovative numerical approach to study railways ballast settlement. Commonly used models representing a moving load need huge computation time. On the other hand, assuming static cyclic loading representation leads to discrepancies. Indeed, it does not conceder particularities of moving load. With this new model we want to avoid the drawbacks of previously developed methods. We developed a steady state algorithm to compute plastic strain in geomaterials and to study behaviour of ballasted railways track with an Eulerian approach. This way we improved model efficiency by drastically reducing computation time while considering mobile load specificities.
Un critere general lisse et convexe est propose pour modeliser le comportement specifique des geo... more Un critere general lisse et convexe est propose pour modeliser le comportement specifique des geomateriaux, particulierement les roches. Ces caracteristiques sont definies par deux fonctions : l'equation du critere dans le plan meridien principal et le ratio d'extension. Elles sont integrees dans une equation garantissant le caractere regulier et convexe de la fonction de charge independamment des fonctions caracteristiques. Cette expression permet la constitution directe d'un modele a partir des essais triaxiaux, en extension et en compression, ainsi que le developpement des formes regularisees correspondant au critere de Coulomb et au critere de Hoek-Brown. Pour calculer numeriquement les deformations plastiques, on demontre l'equivalence entre le probleme numerique (projection sur le point le plus proche) et une configuration geometrique bornee, independante du probleme physique. On peut ainsi constituer des abaques numeriques qui, charges par un logiciel d'el...
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA... more In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA (known at the time as CETE de Lyon), following the fire of September 2008 in che Channel tunnel. Whereas chalk marl was unaffected by the fire even in the most damaged zone, several laboratory test were performed, during the shutdown of the north tunnel. At the request of Eurotunnel society, we determined that the rock behavior was characterized by an extreme sensitivity to water content: • Young Modulus and Uniaxial Compressive are function of water content , with the same power law. • Unless conserved in a fully saturated atmosphere, chalk marl of the Channel tunnel loses water at an important hourly rate and is totally dry in a few days. This experience was useful for the SAFE project: in the first major modification to the Tunnel infrastructure since it was built, 4 SAFE fire-fighting stations were built. They became operational at the end of 2011. Those stations permit now to contain a major fire. The results of rock mechanics tests performed on samples were conform to the observation made a few months before, in a zone characterized by a higher water content.
A general smooth and convex yield function had been proposed , able to model the particular behav... more A general smooth and convex yield function had been proposed , able to model the particular behavior of porous materials, particularly rock materials, that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane. These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. In this paper, further developments of the criterion are made to encompass to modelize the behavior of damaged, weathered or heavily fractured rocks. We identify the functions that allow to develop a smooth version of the generalized Hœk-Brown criterion. So it can be use do predict the behavior of rock masses, relying on identification on intact core sample, and taking into account observations made by geologist and field engineers through the Geological Streng...
While the Mohr-Coulomb criterion is widely used in geotechnics, the Drucker-Prager is common in f... more While the Mohr-Coulomb criterion is widely used in geotechnics, the Drucker-Prager is common in finite element software. Its circular shape is really a great advantage from a numerical point of view, even it is a drawback from a physical point of view. In contrast, the Matsuoka-Nakai criterion seems to best fit material behaviour, particularly with regard to true triaxial tests. Moreover its smooth shape is also closer to the Mohr-Coulomb shape than that of the Drucker-Prager. However, the circular shape of Drucker-Prager allows rapid and straightforward computations of plastic strain, due to the use of the radial return closed form. In contrast, the closest point projection method used to compute plastic strain for other criteria is more complex to implement and requires more computation time. Maiolino and Luong have shown that using the Drucker-Prager criterion as a substitution for a Mohr-Coulomb criterion induces great discrepancies of the friction angle. But in previous work, t...
Computing plastic strain is a crucial issue in finite element methods. This problem is also known... more Computing plastic strain is a crucial issue in finite element methods. This problem is also known as closest point projection. The radial return used for circular models reduces the computations to literal expressions. But in geomechanics, the deviatoric shape of yield functions is generally non circular, so that return mapping algorithm becomes cumbersome and time consuming. Works that will be presented rather focus on a geometric based methods. It will be demonstrated that the numerical problem of closest point projection of the trial stress on the yield surface is equivalent to a geometrical bounded problem. Whereas this property is intuitive, the tools ensuring a straightforward equivalence between the two problems were to be developed. We identify the geometric problem associated to the problem of the closest point projection in the deviatoric plane. The geometric problem is independent from the mechanical one, and can be solved with trigonometric and geometric laws. Those laws...
Cette thèse aborde à la fois des aspects comportementaux et numériques de la réponse mécanique du... more Cette thèse aborde à la fois des aspects comportementaux et numériques de la réponse mécanique du massif rocheux au creusement d'un tunnel. La comparaison de critères existants a mis l'accent sur quelques points clefs, comme la dépendance du critère à la contrainte moyenne et le ratio d'extension. Une fonction de charge, aisément identifiable à partir des essais, au caractère régulier et convexe, capable de tenir compte de la forme de l'enveloppe de Mohr du critère, ainsi que du ratio d'extension, a été proposée : on peut ainsi réaliser des formes régularisées des critères de Mohr-Coulomb et de Hœk-Brown. Le développement de ce nouveau critère a été complété par la proposition d'une méthode d'abaques numériques, accélérant grandement la résolution. Pour le critère proposé, le problème physique est équivalent à un problème purement géométrique, en coordonnées polaires dans le plan. On peut ainsi constituer des abaques numériques qui permettent d'obtenir...
A general smooth and convex yield function is proposed, able to model the particular behavior of ... more A general smooth and convex yield function is proposed, able to model the particular behavior of geomaterials, particularly rock materials that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane. These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. This expression is interesting, because it allows a straightforward development of a constitutive model based on triaxial tests, in extension and compression. It also allows the development of smooth criteria corresponding to the Mohr–Coulomb criterion and the Hoek–Brown criterion, the latter typical of rock mechanics.
In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA... more In this paper, we present the rock mechanics tests performed at Laboratory of Lyons of the CEREMA (known at the time as CETE de Lyon), following the fire of September 2008 in che Channel tunnel. Whereas chalk marl was unaffected by the fire even in the most damaged zone, several laboratory test were performed, during the shutdown of the north tunnel. At the request of Eurotunnel society, we determined that the rock behavior was characterized by an extreme sensitivity to water content: • Young Modulus and Uniaxial Compressive are function of water content , with the same power law. • Unless conserved in a fully saturated atmosphere, chalk marl of the Channel tunnel loses water at an important hourly rate and is totally dry in a few days. This experience was useful for the SAFE project: in the first major modification to the Tunnel infrastructure since it was built, 4 SAFE fire-fighting stations were built. They became operational at the end of 2011. Those stations permit now to contain a major fire. The results of rock mechanics tests performed on samples were conform to the observation made a few months before, in a zone characterized by a higher water content.
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Papers by Siegfried Maiolino
rock materials that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane.
These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. This expression is interesting, because it allows a straightforward development of a constitutive model based on triaxial tests, in extension and compression. It also allows the development of smooth criteria corresponding to the Mohr–Coulomb criterion and the Hoek–Brown criterion, the latter typical of rock mechanics.
rock materials that are characterized by a linear or parabolic Mohr’s envelope, and a particular shape in the deviatoric plane.
These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. This expression is interesting, because it allows a straightforward development of a constitutive model based on triaxial tests, in extension and compression. It also allows the development of smooth criteria corresponding to the Mohr–Coulomb criterion and the Hoek–Brown criterion, the latter typical of rock mechanics.