References of "Collin, Frédéric"
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See detailModeling the strain localization around an underground gallery with a hydro-mechanical double scale model; effect of anisotropy
van den Eijnden, AP; Bésuelle, Pierre; Collin, Frédéric ULg et al

in Computers and Geotechnics (in press)

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See detailThe influence of the rotational hardening rule of yield surface for natural clays: review and comparative study
Ahayan, Sanae ULg; Yin, Zhen-Yu; Kotronis, Panagiotis et al

in Computers and Geotechnics (in press)

Induced anisotropy is a constitutive feature of clays that can be numerically introduced through a proper "Rotational Hardening Rule" allowing the rotation of the yield and the potential plastic surfaces ... [more ▼]

Induced anisotropy is a constitutive feature of clays that can be numerically introduced through a proper "Rotational Hardening Rule" allowing the rotation of the yield and the potential plastic surfaces in the stress space. In this paper, rotational hardening rule of yield surface for clays are first reviewed. Then, five typical rotational hardening rules are selected and compared through simulating drained triaxial tests of two Finnish clays. Furthermore, finite element simulations of a strip rigid footing considering different rotational hardening rules together with the case of isotropic yield surface without rotation are carried out in order to study the consequences of the isotropy assumption and the influence of the rotational hardening rule on the behavior of shallow foundation. [less ▲]

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See detailOn the Variable Dilatancy Angle in Rocks Around Underground Galleries
Salehnia, Fatemeh ULg; Collin, Frédéric ULg; Charlier, Robert ULg

in Rock Mechanics & Rock Engineering (2016)

Correct estimation of the dilatant behavior of a rock has an essential role in a realistic numerical simulation of the fracturing threshold during the rock deformation process and its post-failure ... [more ▼]

Correct estimation of the dilatant behavior of a rock has an essential role in a realistic numerical simulation of the fracturing threshold during the rock deformation process and its post-failure response, based on experimental and field observations. This importance has been poorly treated in most of the numerical analyses dealing with the rock engineering common problems such as deep excavations. The dilatancy angle as a commonly used parameter for describing the dilatation response of a rock is mostly simplified to be a constant value. Contrarily, a literature review declares the inadequacy of this approach in those rock mechanics applications. In the present paper, a new formula for considering the variable dilatancy angle is presented which relates this parameter to the plastic shear strain in the course of a loading procedure. It is aimed at characterizing an evolution of the dilatant or contracting volumetric response of a rock as well as giving the possibility to simulate a dilatant/contracting transitional behavior. The model is applied to simulate the development of strain localization, in shear band mode, within the inevitable excavation damaged zone created around an underground opening in rock. It is illustrated that using the model of variable dilatancy angle in a deep excavation modeling could help to better reproduce the fractures development around the opening in the course of tunneling. [less ▲]

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See detailNumerical modeling of coupled thermal-hydro-mechanical behavior of GMZ bentonite in the China-Mock-up test
Zhao, Jingbo; Chen, Liang; Collin, Frédéric ULg et al

in Engineering Geology (2016), 214

Gaomiaozi (GMZ) bentonite is currently considered as themost suitable buffermaterial for high-level radioactive waste geological repository in China. To investigate the long-term performance of GMZ ... [more ▼]

Gaomiaozi (GMZ) bentonite is currently considered as themost suitable buffermaterial for high-level radioactive waste geological repository in China. To investigate the long-term performance of GMZ bentonite under repository conditions, a large scale mock-up test has been carried out since 2011. In the test, a hydration systemand an electrical heater were employed to simulate the Thermal-Hydro-Mechanical (THM) coupled conditions near a repository. In this work, a numerical study is performed to reproduce the experimental data obtained in the first three years of the China-Mock-up experiment. The principle THM characteristics and parameters of the bentonite are presented. On this basis, a THM coupled constitutive model is introduced. With the proposed model, numerical simulations of the China-Mock-up test are carried out using LAGAMINE. The numerical data of temperature, relative humidity, and swelling pressure of the GMZ compacted bentonite are compared with the experimental ones.We discuss the effect of the balance between the drying effect and water penetration process on the THM behavior of the GMZ bentonite. The good agreement between the predicted and experimental results suggests that the proposed model can reproduce the fundamental behavior of GMZ compacted bentonite under coupled THM conditions. [less ▲]

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See detailEffect of rotational hardening rule on the behavior of clayey soils
Ahayan, Sanae ULg; Kotronis, Panagiotis; Collin, Frédéric ULg et al

Scientific conference (2016, October 26)

Induced anisotropy is a constitutive feature of clays that can be numerically introduced through a proper "Rotational Hardening Rule" allowing the rotation of the yield and the potential plastic surfaces ... [more ▼]

Induced anisotropy is a constitutive feature of clays that can be numerically introduced through a proper "Rotational Hardening Rule" allowing the rotation of the yield and the potential plastic surfaces in the stress space. In this presentation, rotational hardening rule of yield surface for clays are first reviewed. Then, two typical rotational hardening rules are selected and compared through simulating drained triaxial tests of two Finnish clays. Furthermore, finite element simulations of a strip rigid footing considering different rotational hardening rules together with the case of isotropic yield surface without rotation are carried out in order to study the consequences of the isotropy assumption and the influence of the rotational hardening rule on the behavior of shallow foundation. [less ▲]

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See detailBounding surface plasticity model for natural clays
Ahayan, Sanae ULg; Yin, Zhen-Yu; Kotronis, Panagiotis et al

Conference (2016, October 26)

Natural soft clay exhibits a considerable degree of anisotropy as a result of its past sedimentation and consolidation history. It also tends to have significant inter-particle bonding, which affects its ... [more ▼]

Natural soft clay exhibits a considerable degree of anisotropy as a result of its past sedimentation and consolidation history. It also tends to have significant inter-particle bonding, which affects its mechanical behavior. The natural structure of in-situ soils makes their behavior different from that of a reconstituted material. In fact, most clays lose a proportion of their strength when remoulded. Various authors proposed anisotropic elastoplastic soil models allowing the yield surface to rotate with the stress history. These models have a “rotational hardening law" which relates the change of the inclination of the yield surface to the current soil state and to the increments of the plastic volumetric and/or shear strain, [Sekiguchi and Otha (1977)], [Hashiguchi and Chen (1998)], [Wheeller et al (2003)]… Other authors combine the plastic anisotropy with destructuration effects observed in soft sensitive soils by assuming that the size and /or the position of the center of the yield surface depends on the amount of the structural soil degradation. These models use an additional isotropic hardening law that relates the size and/or the position of the yield surface of the intact sample to that of the reconstituted one [Nova et al (2003)]. The previous models provide little or no flexibility when it comes to describe the change of the plastic modulus with the loading direction as they are unable to produce a smooth degradation of the stiffness, being single yield surface models. A way to improve this behavior is to introduce the “bounding surface plasticity” theory, initially developed by Dafalias [Dafalias and Herrmann 1986]. Unlike a single yield surface model, the bounding surface theory allows a smooth transition of stresses within and on the bounding surface. The mean feature of this concept is that the actual stress is mapped to the imaginary stress on the bounding surface. The distance between the real and imaginary stress, which is called the “ function distance ”, is used to specify the plastic modulus. This work presents a bounding surface plasticity model for natural and structured clays based on the critical state theory. A novel rotational hardening rule for clays is presented, and a hardening function distance is introduced to describe the evolution of the bounding surface. Validation of the model is provided by drained and undrained tests of Scottish and Finnish intact and reconstituted clays [Kastunnen 2008]. Finally, finite element simulations of a foundation considering the formulated constitutive law are presented. [less ▲]

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See detailDetailed characterization of the Late Pleistocene loess sequence stratigraphy of Remicourt (Hesbaye region, Belgium) with cone penetration tests
Delvoie, Simon ULg; Boulvain, Frédéric ULg; Charlier, Robert ULg et al

in Geologica Belgica (2016), 19(3-4), 281-289

Cone penetration tests (CPT) and drilling results are used to characterize the Middle Belgium loess sequence. A two scale study has been realized in the Hesbaye region (Belgium). The study on a regional ... [more ▼]

Cone penetration tests (CPT) and drilling results are used to characterize the Middle Belgium loess sequence. A two scale study has been realized in the Hesbaye region (Belgium). The study on a regional scale was performed along a 18 km long section of the high-speed railway Liège-Brussels. About 230 tests were compiled. Results show the loess thickness is very variable and can locally reach 20 m. Tertiary deposits become continuous and they rapidly thicken from Waremme to the West. The lower surface of the Tertiary deposits is characterized by a 0.3% apparent dipping to the NW. The dipping likely results from the Ardenne Massif uplift. The local scale study focuses on the site of Remicourt located along the high-speed railway. 24 CPT tests have been carried out very close to a series of archaeological trenches. The analysis shows penetrometers are able to define some stratigraphic markers within the loess layer. The most identifiable marker is stratigraphically located around the transition between the Humiferous Complex of Remicourt and the Rocourt Pedocomplex. The lens-shape of the loess ridge is also confirmed by the penetrometers’ interpretation. Furthermore, the 3D morphology of each stratigraphic marker can be estimated. These results offer interesting perspectives for the investigation of the loess sequence related to archaeological applications. [less ▲]

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See detailSynthèse des données gétechniques nécessaires à l'étude de la stabilité de cinq terrils à risque en région wallonne - phase2
Delvoie, Simon ULg; Collin, Frédéric ULg

Report (2016)

Dans le cadre d’un recensement des terrils situés en Région wallonne et pouvant présenter des risques de stabilité sur le court et le long terme, l’ISSeP a chargé le Laboratoire de Géotechnologies de ... [more ▼]

Dans le cadre d’un recensement des terrils situés en Région wallonne et pouvant présenter des risques de stabilité sur le court et le long terme, l’ISSeP a chargé le Laboratoire de Géotechnologies de l’Université de Liège, représenté par Ir. F. COLLIN et S. DELVOIE, de réaliser une étude géotechnique préliminaire. Les objectifs de ce travail sont tout d’abord de recenser les informations disponibles sur le sous-sol aux environs immédiats des terrils. Les données recueillies sont ensuite exploitées par des outils informatiques SIG et seront par la suite utilisées dans l’évaluation du risque d’instabilité, réalisée par l’ISSeP. Ce travail documentaire est également complété par une inspection sur le terrain de chaque terril étudié. Les terrils faisant partie de l’étude géotechnique sont repris dans la liste ci-dessous : - Argenteau Ancien et Argenteau Nouveau – OBID 578-579 – L6 et L7 - Saint-Placide – OBID 343 – B60 - 14-17 et Siège social – OBID 5151 – B80-1 - Héribus – OBID 557 – B88-1 - Crachet 7/12 – OBID 286 – B111 [less ▲]

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See detailL'effet de l'écrouissage rotationnel sur le comportement des sols argileux
Ahayan, Sanae ULg; Yin, Zhen-Yu; Kotronis, Panagiotis et al

Conference (2016, May 25)

Induced anisotropy is a constitutive feature of clays that can be introduced through a proper "Rotational hardening law" allowing the rotation of the yield and the potential plastic surfaces in the stress ... [more ▼]

Induced anisotropy is a constitutive feature of clays that can be introduced through a proper "Rotational hardening law" allowing the rotation of the yield and the potential plastic surfaces in the stress space. Two rotational hardening laws are studied in this paper. Validation is provided using the results of a drained triaxial test of a Finnish clay. Finite Elements simulations of a circular rigid footing considering an isotropic and anisotropic constitutive laws are presented. The objective is firstly to identify the influence of the isotropy assumption in geotechnical design and secondly to study the effect of different hardening laws on the foundation behavior. [less ▲]

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See detailIn situ and laboratory mechanical characterization of a loess sequence from Middle Belgium
Delvoie, Simon ULg; Charlier, Robert ULg; Collin, Frédéric ULg

Conference (2016, May 25)

A 10 m thick loess (aeolian silt) layer located beside the Romont quarry (Eben-Emael, Middle Belgium) has been investigated in order to characterize the mechanical behaviour of the silty material. Cone ... [more ▼]

A 10 m thick loess (aeolian silt) layer located beside the Romont quarry (Eben-Emael, Middle Belgium) has been investigated in order to characterize the mechanical behaviour of the silty material. Cone penetration tests (CPT) have been performed with different cones (M1-type, M2-type and electric) in order to evaluate the influence of the cone on the mechanical behaviour interpretation. Concurrently, laboratory tests have been performed on undisturbed samples from core drillings. Laboratory tests consist of a physical characterization (grain size distribution, Atterberg limits) and a mechanical characterization (oedometer tests). This comprehensive investigation study focuses on the comparison of the loess characterization between in situ and laboratory approaches. CPT-based soil behaviour type charts are analyzed and compared with the Unified Soil Classification System. Many relations also exist in the literature between parameters obtained from CPT results and from laboratory tests. The study explores the existing relations between the cone resistance and the oedometer constrained modulus in order to verify the related coefficients proposed in the literature for silty material. [less ▲]

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See detailAccurate measurement of radius evolution as a function of direction in 3D images
Plougonven, Erwan ULg; Hubert, Julien ULg; Collin, Frédéric ULg et al

Poster (2016, May 11)

Very often the reason for using of X-Ray tomography in a research project is to measure the evolution of some geometrical characteristic. The sought characteristic may be explained in simple words like ... [more ▼]

Very often the reason for using of X-Ray tomography in a research project is to measure the evolution of some geometrical characteristic. The sought characteristic may be explained in simple words like size, shape, or distance, but in practice measures based on these notions can have a complex implementation. We present a simple problem, measuring the evolution of radius in a cylindrical sample (a common shape for sample preparation for tomography) and how this value differs according the direction in which we look, when such evolution is known to be anisotropic. The solution is not unique, but we show that a naïve manual approach are not accurate enough, and how even a simple geometric notion such as radius needs a thorough definition in relation to its applicability to 3D image analysis. We extend the argument to how a good understanding of the notions and algorithms used in the quantification of geometrical characteristics can directly affect the pertinence and representativity of the results. [less ▲]

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See detailModeling of granular solids with computational homogenization: Comparison with Biot's theory
Marinelli, F.; Van den Eijnden, AP; Sieffert, Y. et al

in Finite Elements in Analysis and Design (2016), 119

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See detailEvaluation de la stabilité d'une paroi rocheuse à Flémalle
Delvoie, Simon ULg; Collin, Frédéric ULg

Report (2016)

La caractérisation détaillée du massif rocheux a été réalisée à partir de mesures in situ et d'observations. Ces données sont ensuite utilisées dans l'analyse de stabilité du massif rocheux. Un traitement ... [more ▼]

La caractérisation détaillée du massif rocheux a été réalisée à partir de mesures in situ et d'observations. Ces données sont ensuite utilisées dans l'analyse de stabilité du massif rocheux. Un traitement adéquat de la paroi est finalement proposé afin de minimiser les projections de blocs rocheux sur d'éventuels bâtiments sur le moyen et le long terme. [less ▲]

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See detailDrying induced shrinkage of Boom Clay: an experimental investigation
Prime, Noémie; Levasseur, Séverine ULg; Miny, Laurent et al

in Canadian Geotechnical Journal (2016), 53(3), 396-409

Drying induced shrinkage of geomaterials may have a strong effect on geostructure stability and deformation. Settlement of foundations, fracture opening on slopes, roads, tunnel walls may be due to drying ... [more ▼]

Drying induced shrinkage of geomaterials may have a strong effect on geostructure stability and deformation. Settlement of foundations, fracture opening on slopes, roads, tunnel walls may be due to drying shrinkage. However, there is still a lack of knowledge concerning shrinkage evolution in time and shrinkage propagation within the material. In this study, the shrinkage of a specific clayey rock, Boom Clay, under drying conditions is experimentally investigated. This rock is a deep geological formation which is under study for high-level and long-life radioactive waste storage in Belgium. Two experimental campaigns are here presented. The first one, based on vapour equilibrium drying technique and completed by sample size manual measurement, aims to characterize the material shrinkage in balanced states. The second one, based on convective drying technique completed by shape monitoring using X-ray tomography, aims to analyse how shrinkage develops before reaching a steady state. Both approaches put in evidence the shrinkage anisotropy of this structurally bedded rock, with a ratio around 2 between the direction of maximum strains and the direction of minimum strains. However, the two drying techniques also provide complementary results, as the relation between the amount of shrinkage and the retention curve (for the uniform drying imposed with saline solutions) and the kinetics of shrinkage propagation inside the material (for the non-uniform drying imposed with air convection). [less ▲]

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See detailDesiccation cracks formation in clay-barrier for nuclear waste disposal
Hubert, Julien ULg; Prime, Noémie; Plougonven, Erwan ULg et al

Conference (2016, February 16)

In geotechnical engineering, the desiccation cracking of soil is commonly observed. This phenomenon is detrimental to the behavior of earth material and earth structure. Desiccation cracks can lead to the ... [more ▼]

In geotechnical engineering, the desiccation cracking of soil is commonly observed. This phenomenon is detrimental to the behavior of earth material and earth structure. Desiccation cracks can lead to the overall failure of many geotechnical structures: • They can affect the slope stability of earth dams or embankments; • They can initiate internal erosion of embankments due to water flow through the cracks; • They can compromise the efficiency of soil barriers such as landfill liners and top covers. Nowadays, the storage of nuclear waste in deep impermeable geological layers is considered. These storages are based on the multi-barrier principle, the last of which being the host rock, typically a clayey material. In this context, maintaining the very low hydraulic conductivity of the host rock is crucial. Unfortunately, the ventilation of excavated galleries causes convective drying of the host material and can lead to crack formation. This work aims to understand in which conditions exactly, during convective drying, does cracking occur in clayey materials. An experimental campaign has been carried out to characterize the drying behavior of Boom clay which is the host rock at the underground research facility in Mol (Belgium). X-Ray micro-tomography has been used to analyze crack development as well as shrinkage. The experiments are used to calibrate the transfer parameters of a convective drying law based on the limit layer model. This calibration is based on agreement of the drying kinetics. A numerical study is then performed and aims at reproducing the behavior observed during the experiments. A thermo-hydro-mechanical coupled model is used to determine the stress distribution during the drying and a tensile failure criterion is suggested to predict crack genesis. Simulations are performed using the in-house built FEM code LAGAMINE. [less ▲]

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See detailNumerical modeling of the long term behavior of Municipal Solid Waste in a bioreactor landfill
Hubert, Julien ULg; Xianfeng, Liu; Collin, Frédéric ULg

in Computers and Geotechnics (2016), 72

This paper presents a thermo-hydro–biochemo-mechanical model for simulating the long term behavior of Municipal Solid Waste (MSW) in a bioreactor landfill, in which the multi-physics coupling mechanism ... [more ▼]

This paper presents a thermo-hydro–biochemo-mechanical model for simulating the long term behavior of Municipal Solid Waste (MSW) in a bioreactor landfill, in which the multi-physics coupling mechanism plays a dominant role. In the model, a two-stage anaerobic biochemical model based on McDougall’s formulation is incorporated into a fully coupled thermo-hydro-mechanical models originally developed for unsaturated porous medium. The mechanical model is a modified Camclay model allowing for biochemical hardening/softening, while the thermal model is described by a classical energy balance equation with a source term accounting for the heat generation from the biodegradation of organic matter. The hydraulic model is an unsaturated flow model using Richard’s equation. The derived coupled model is implemented into an in-house built multi-physics finite element code. Finally, numerical simulations were performed to illustrate the capability of the proposed model for estimating long-term settlement of a bioreactor landfill and its aptitude as a landfill management tool for optimizing the landfill operation [less ▲]

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