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 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 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; 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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See detailWater retention behaviour of compacted bentonites: experimental observations and constitutive model
Dieudonné, Anne-Catherine ULg; Gatabin, Claude; Talandier, Jean et al

in Delage, Pierre; Cui, Yu-Jun; Ghabezloo (Eds.) et al 3rd European Conference on Unsaturated Soils – “E-UNSAT 2016” (2016)

Bentonite-based materials are studied as potential barriers for the geological disposal of radioactive waste. In this context, the hydro-mechanical behaviour of the engineered barrier is first ... [more ▼]

Bentonite-based materials are studied as potential barriers for the geological disposal of radioactive waste. In this context, the hydro-mechanical behaviour of the engineered barrier is first characterized by free swelling conditions followed by constant volume conditions. This paper presents an experimental study conducted in order to characterize the water retention behaviour of a compacted MX-80 bentonite/sand mixture. Then, based on observations of the material double structure and the water retention mechanisms in compacted bentonites, a new water retention model is proposed. The model considers adsorbed water in the microstructure and capillary water in the aggregate-porosity. The model is calibrated and validated against the experimental data. It is used for better understanding competing effects between volume change and water uptake observed during hydration under free swelling conditions. [less ▲]

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See detailA FE2 modelling approach to hydromechanical coupling in cracking-induced localization problems
Van den Eijnden, AP; Bésuelle, Pierre; Chambon, René et al

in International Journal of Solids and Structures (2016), 97

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See detailSuitability of soils and river deposits from Marrakech for the manufacturing of earthenware
El Boudour El Idrissi, Hicham ULg; Daoudi, Lahcen; El Ouahabi, Meriam ULg et al

in Applied Clay Science (2016), 129

This paper investigates the suitability of clayey materials originating from semi-arid soil and river sediments, used by potters in the Agafay region for the manufacture of ceramic products. The clay ... [more ▼]

This paper investigates the suitability of clayey materials originating from semi-arid soil and river sediments, used by potters in the Agafay region for the manufacture of ceramic products. The clay samples were subjected to particle-size analysis, X-ray diffraction and X-ray fluorescence to investigate their physical, mineralogical and chemical characteristics respectively. The physical behaviour of the intermediate products was studied at the shaping and drying stages of the ceramics manufacturing process through the Atterberg limits and the plot of the Bigot curve respectively. The final product characteristics were determined through porosity tests, flexural and compressive strengths tests. Based on results obtained, the raw materials turn out to be suitable characteristics for the manufacture of earthenware products. The application of the suggested recommendations is worthy for the improvement of the products based on such raw materials. [less ▲]

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See detailEtude de la séquence stratigraphique des loess de la carrière de Romont (Eben-Emael, Belgique) par une campagne géotechnique
Delvoie, Simon ULg; Pirson, Stéphane ULg; Charlier, Robert ULg et al

in Notae Praehistoricae (2016), 36

The Romont quarry is recently considered as a new type section for the Middle Belgium loess deposits. The site displays a nearly 10 m thick loess sequence mainly dating from the Upper Pleistocene. The ... [more ▼]

The Romont quarry is recently considered as a new type section for the Middle Belgium loess deposits. The site displays a nearly 10 m thick loess sequence mainly dating from the Upper Pleistocene. The Rocourt Pedocomplex, the Humiferous Complex of Remicourt, the Malplaquet Soil and the Nagelbeek Tongued Horizon are especially well developed. Classical approaches to study the loess sequence need observable sections. Unfortunately these sections are rare in Middle Belgium, often temporary and not deep enough. To identify reference horizons, archaeologists and geologists use to resort to hand auger sampling techniques. Investigation of loess by cone penetration tests could offer an alternative to the lack of outcrops and could be used complementary to hand drilling techniques. This study focuses on a methodology to approach as a first step the loess sequence to identify the presence or not of some layers and their extension. The investigation campaign performed on the site of Romont aims to define reference horizons based on mechanical properties by comparison with an observable outcrop. Then 16 cone penetration tests have been realized behind the working face. The campaign results reveal the existence of some horizons into the loess sequence. The transition between the Humiferous Complex of Remicourt and the Rocourt Pedocomplex is the most noticeable horizon. These two pedostratigraphic units are important due to the presence of archaeological materials in Middle Belgium and borderlands. Closer to the surface the Nagelbeek Tongued Horizon and the decarbonation limit are also highlighted from results of the geotechnical campaign. [less ▲]

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