References of "Collin, Frédéric"
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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 (in press), 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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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; Collin, Frédéric ULg; 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 detailPermeability evolution and water transfer in the excavation damaged zone of a ventilated gallery
Pardoen, Benoît ULg; Talandier, Jean; Collin, Frédéric ULg

in International Journal of Rock Mechanics & Mining Sciences (2016), 85

The fluid transfers occurring around underground galleries are of paramount importance when envisaging the long-term sustainability of underground structures for nuclear waste disposal. These transfers ... [more ▼]

The fluid transfers occurring around underground galleries are of paramount importance when envisaging the long-term sustainability of underground structures for nuclear waste disposal. These transfers are mainly conditioned by the behaviour of the surrounding material and by its interaction with the gallery air. The hydro-mechanical behaviour of the excavation damaged zone, which develops around galleries due to the drilling process, is thenceforward critical because it is composed of fractures having a significant irreversible impact on flow characteristics and transfer kinetics. Besides, the material interaction with the gallery air may engender water drainage and desaturation. Thus, a gallery air ventilation experiment, preceded by its excavation, is numerically modelled in an unsaturated argillaceous rock to study its influence on hydraulic transfers. The fractures are numerically represented with shear strain localisation bands by means of a microstructure enriched model including a regularisation method. The impact of fracturing on the transport properties is addressed by associating the intrinsic permeability increase with mechanical deformation which is amplified in the strain localisation discontinuities. Such dependence permits us to reproduce a significant permeability increase of several orders of magnitude in the excavation damaged zone, in agreement with available experimental measurements. After the excavation, the hydraulic transfers are studied through the reproduction of a gallery air ventilation experiment that implies drainage and desaturation of the surrounding rock. These transfers depend on liquid water and water vapour exchanges at gallery wall that are introduced through a non-classical boundary condition. The model prediction successfully captures the drainage and desaturation kinetics of undisturbed and damaged rock. [less ▲]

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See detailCompeting effects of volume change and water uptake on the water retention behaviour of a compacted MX-80 bentonite/sand mixture
Gatabin, Claude; Talandier, Jean; Collin, Frédéric ULg et al

in Applied Clay Science (2016), 121-122

Bentonite-based materials have been 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 have been 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 (as a consequence of the progressive filling of technological gaps) 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. The water retention properties upon wetting were investigated under both free swelling and constant volume conditions. In the high suction range, the water content was not influenced by the imposed volume constraints. On the contrary, swelling significantly affected the water retention behaviour at low suctions, and the quantity of water stored was higher under free swelling conditions than it was under prevented swelling. In this case, competing effects between bentonite swelling and water uptake did not lead to an increase of the degree of saturation upon wetting, as it was observed for samples wetted under constant volume conditions. The influence of the very strong hydro-mechanical coupling is further discussed. [less ▲]

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See detailEssentials of actions
Cerfontaine, Benjamin ULg; Collin, Frédéric ULg; Denoël, Vincent ULg et al

Learning material (2015)

This document deals with the philosophy of safety in civil engineering structures, including loads and load combinations to be applied when designing a structure. It contains general concepts that are ... [more ▼]

This document deals with the philosophy of safety in civil engineering structures, including loads and load combinations to be applied when designing a structure. It contains general concepts that are presented and discussed as well as values for some important input data that can be used as order of magnitude in the initial phase of a project. [less ▲]

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See detailNumerical modelling of transient cyclic vertical loading of suction caissons in sand
Cerfontaine, Benjamin ULg; Collin, Frédéric ULg; Charlier, Robert ULg

in Geotechnique (2015), 65(12),

This paper presents numerical investigations of the monotonic and cyclic behaviours of suction caissons upon vertical transient loading. Both drained and partially drained conditions are investigated ... [more ▼]

This paper presents numerical investigations of the monotonic and cyclic behaviours of suction caissons upon vertical transient loading. Both drained and partially drained conditions are investigated. Monotonic compression and traction simulations are carried out to qualitatively compare results with the literature and validate the model. They highlight the different modes of reaction of the caisson to both compression and traction loading. A sensitivity analysis points out the strong influence of some parameters on the resistance of the caisson but also on the failure mechanism. The transient behaviour of the caisson upon different kinds of cyclic load signals is analysed. Results reproduce the settlement and pore water pressure accumulations observed during experiments. The influence of the key design parameters on the settlement accumulation is also assessed. Finally a cyclic diagram is proposed to describe the evolution of the final settlement upon different magnitudes of loading. [less ▲]

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See detailShear banding modelling in cross-anisotropic rocks
Pardoen, Benoît ULg; Seyedi, D.M.; Collin, Frédéric ULg

in International Journal of Solids and Structures (2015), 72

Sedimentary geomaterials such as rocks frequently exhibit cross-anisotropic properties and their behaviour depends on the direction of loading with respect to their microstructure. As far as material ... [more ▼]

Sedimentary geomaterials such as rocks frequently exhibit cross-anisotropic properties and their behaviour depends on the direction of loading with respect to their microstructure. As far as material rupture is concerned, localised deformation in shear band mode appears generally before cracks and material failure. The influence of cross-anisotropy on the shear strain localisation remains an important issue and is investigated in the present study. To do so, a constitutive elastoplastic cross-anisotropic model that includes anisotropy both on the elastic and plastic characteristics is defined. For the plastic part of the model, the anisotropy of a strength parameter is introduced with a microstructure fabric tensor. Then, the fractures are modelled with finite element methods by considering the development of shear strain localisation bands and an enriched model is used to properly reproduce the shear banding. The cross-anisotropy influence on shear banding is studied through numerical applications of small and large-scale geotechnical problems that engender fractures. The two considered applications are a plane-strain biaxial compression test and an underground gallery excavation. The numerical results provide information about the influence of cross-anisotropy on the appearance and development of shear bands. It has been noticed, among other observations, that the material strength vary with the loading direction and that the development and the shape of the excavation fractured zone that develops around a gallery is strongly influenced by the material anisotropy. [less ▲]

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See detailTu gme 10: Efficiency of shaft sealing for co2 sequestration in coal mines
Bertrand, François ULg; Charlier, Robert ULg; Collin, Frédéric ULg et al

in International Workshop on Geomechanics and Energy: The Ground as Energy Source and Storage (2015, October 13)

This work examined the efficiency of a shaft sealing system for the CO2 sequestration in abandoned coal mines. The particular case of the coal mine of Anderlues was considered. The performed simulation ... [more ▼]

This work examined the efficiency of a shaft sealing system for the CO2 sequestration in abandoned coal mines. The particular case of the coal mine of Anderlues was considered. The performed simulation took into account the anisotropic behaviour of shale and the presence of coalbeds. [less ▲]

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See detailCaractérisation géologique et mécanique d'une paroi rocheuse à Wegnez en vue de son excavation et de sa stabilisation
Delvoie, Simon ULg; Bertrand, François ULg; Collin, Frédéric ULg

Report (2015)

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

La caractérisation détaillée du massif rocheux a été réalisée à partir de mesures in situ et en laboratoire. Ces données sont ensuite utilisées dans l'analyse de stabilité du massif rocheux (stabilité d'ensemble et stabilité de blocs selon un joint de discontinuité). L'étude présente également une analyse en vue d'estimer la ou les techniques d'excavation adéquates. [less ▲]

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See detailRetour en grâce du grisou
Bertrand, François ULg; Charlier, Robert ULg; Collin, Frédéric ULg

Diverse speeche and writing (2015)

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See detailCoupled modeling of Excavation Damaged Zone in Boom clay: Strain localization in rock and distribution of contact pressure on the gallery’s lining
Salehnia, Fatemeh ULg; Collin, Frédéric ULg; Li, Xiang Ling et al

in Computers and Geotechnics (2015), 69

Around galleries excavated at depth in geological media, the creation of a damaged zone with significant irreversible deformation is generally unavoidable. In the case of a geological disposal system for ... [more ▼]

Around galleries excavated at depth in geological media, the creation of a damaged zone with significant irreversible deformation is generally unavoidable. In the case of a geological disposal system for high-level radioactive waste, the resulting change in the host rock properties in this damaged zone may potentially be important with respect to the long-term evolution and the performance of that system. In this context, predicting the extent of the so-called Excavation Damaged Zone (EDZ) and, possibly, the fractures' network topology remains a challenge. This study is aimed to simulate numerically the extension of this zone at the large scale's excavation, around the Connecting gallery (HADES URL, Mol, Belgium), in Boom clay host rock through analyzing the evolution of strain localization in shear bands mode. To realistically model the involved phenomena, the concrete lining is considered on the gallery wall highlighting its impacts on the evolution of convergence and EDZ around the gallery. The focus of the current paper is made on analyzing the coupled hydro-mechanical behavior of Boom clay host rock during and after the gallery excavation with respect to the evolution of localized shear bands around the gallery. This study is accompanied by the analysis of the contact mechanism on the interface between the clay massive and the lining. The obtained results reveal some interesting features regarding the contact phenomenon relatively to the evolution pattern of shear bands within the clay around the gallery. To assess the reliability of the proposed approach, a discussion on some in-situ observations during the gallery's construction is also performed based on which a good agreement is found between the in-situ evidence and simulated results. [less ▲]

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See detailPrediction of the excavation damaged zone in Callovo-Oxfordian claystone using a coupled second gradient model
Collin, Frédéric ULg; Pardoen, Benoît ULg

Scientific conference (2015, July 23)

The solution currently studied in France for long-term management of radioactive waste is the repository in deep argillaceous geological media with low permeability. The drilling of underground galleries ... [more ▼]

The solution currently studied in France for long-term management of radioactive waste is the repository in deep argillaceous geological media with low permeability. The drilling of underground galleries in these clayey rocks induces damage propagation in the surrounding medium. This excavation process creates a damaged zone, in which the material properties are modified. The prediction of the fracture structure and material properties evolution within this zone is a major issue especially in the context of underground disposal. Experimental works have highlighted that the damage around galleries in Callovo-Oxfordian claystone is localized and develops mainly as extensional and shear fractures. We propose to model these shear fractures as a strain localisation process in the mode of a shear band. In order to properly represent the shear strain localisation behaviour, an enhanced model introducing a regularization method and an internal length scale is needed. Among the different regularization methods, the coupled second gradient local model is chosen. To illustrate the development of the damaged zone, a two-dimensional plane strain state hydro-mechanical modelling of a gallery excavation is performed (Lagamine code, ULg) for two orientations of the gallery in the Callovo-Oxfordian claystone. Firstly, a gallery oriented along the minor horizontal principal stress is considered. In this direction, the anisotropy of the stress state in the plane perpendicular to the gallery is the predominant factor leading to the elliptical shape of the damaged zone, with a significantly larger extent in the vertical direction. Secondly, a gallery oriented along the major horizontal principal stress is modelled. The stress state in the plane perpendicular to the gallery is quasi-isotropic and does not lead to shear strain localisation unless the material anisotropy is considered. Moreover, the modelling provides information about the fracture structure and evolution around the gallery. It exhibits a chevron fracture pattern corresponding to in situ experimental measurements of shear fractures for both considered gallery orientations. [less ▲]

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See detailIdentification of the main parameters controlling the plasticity of ceramic pastes: The case study of the Marrakech region (Morocco)
El Boudour El Idrissi, Hicham ULg; Daoudi, Lahcen; Fontaine, François ULg et al

Poster (2015, June 07)

Numerous traditional ceramic workshops occur within a range of 10 to 80 km around the city of Marrakech. Our study aims to identify the main parameters controlling the plasticity of pastes used by the ... [more ▼]

Numerous traditional ceramic workshops occur within a range of 10 to 80 km around the city of Marrakech. Our study aims to identify the main parameters controlling the plasticity of pastes used by the artisans. To reach this goal, we characterize by X-ray diffraction, granulometry and plasticity index (PI) the local raw clayey material. The investigation of 26 whole pastes shows the dominance of quartz (20 to 50%) and clay minerals (25 to 60%) with K-feldspar (2 to 17%), plagioclase (2 to 25%), calcite (0 to 18%), dolomite (0 to 15%), goethite (0 to7%) and trace of hematite and anhydrite (< 3%). Amphibole occurs in trace (< 5%) but only in some samples. The clay minerals are diversified, including illite (10 to 40%), kaolinite (2 to 15%), mixed-layer (ML) (0 to 10%), smectite, vermiculite and chlorite (0 to 5%), and pyrophyllite-talc association (0 to 8%). Sepiolite (12%) is only present in one paste. The grain size is made by variable proportions of sand (5 to 65%), silt (12 to 53%) and clayey fraction (18 to 66%). The Plasticity index (PI) indicates the presence of two principals groups of pastes. (1) The first group is characterized by PI values ranging between 15 to 18. Their moderate plasticity behavior is related either to the low rate of clayey fraction and/or to the absence of plastic clays like smectites and mixed layer with smectitic sheets. (2) The PI of second group ranges between 20 to 32. The high plasticity values are influenced by the presence of specific clayey minerals like talc-pyrophyllite or sepiolite, or by the high content of smectite plus smectitic mixed-layers within the clayey (< 2 micron) fraction. Only one sample without any of these plastic minerals but with a high content of clayey fraction is characterized by a high PI value (24). We concluded that the workability of ceramic paste in Marrakech region is controlled by a combination of factors, dominated by the grain size distribution and the content in plastic clay minerals within the fine fraction. [less ▲]

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See detailMechanical approach for the characterization of loess deposits from the CBR’s Romont quarry (Eben-Emael, Belgium) and correlations with loess stratigraphy
Delvoie, Simon ULg; Boulvain, Frédéric ULg; Cerfontaine, Benjamin ULg et al

Conference (2015, June 01)

Aeolian silts (loess) are near surface deposits covering about 10% of the continent surfaces . Therefore a good knowledge of their mechanical behavior is an issue for designing subsurface engineering ... [more ▼]

Aeolian silts (loess) are near surface deposits covering about 10% of the continent surfaces . Therefore a good knowledge of their mechanical behavior is an issue for designing subsurface engineering structures. Usually this material is considered as homogeneous for an engineering point of view. Aeolian silt deposits are continuously well developed in Hesbaye Region (Belgium) reaching locally 20m thick (see document in attachment). They are mainly related to the last interglacial (Eemian) and glacial (Weichselian) periods . Nevertheless the pedostratigraphical, chronostratigraphical and paleoclimatic approaches have shown these silt deposits are usually composed of a series of paleosoils (i.e. Rocourt soil, Humiferous Complex of Remicourt, Harmignies Soil, Nagelbeek Tongued Horizon) interbedded with stratified or homogeneous aeolian silt layers. This study aims to characterize the variability of the in situ mechanical characteristics of the loess deposits from Hesbaye Region at the site scale and at the laboratory scale. Cone penetration tests (CPT), electrical resistivity tomographies (ERT) and drillings have been performed through a 10m thick loess layer in an investigation site located close to the CBR’s Romont quarry (Eben-Emael, Belgium) . Continuous undisturbed silt samples from drillings have been physically (granulometry, Atterberg limits, water content, organic matter content, carbonate content) and mechanically (oedometer test, triaxial test) characterized at the laboratory. Mechanical behavior and physical characteristics have underlined a series of layers with variable mechanical properties through depth. Some of these layers correlated with a detailed stratigraphy cross-section close to the investigation site could correspond to well-known paleosoils. [less ▲]

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See detailEstimation de tassements pour le site « Realex Tower »
Bertrand, François ULg; Collin, Frédéric ULg

Report (2015)

Rapport d'expertise de tassement sur base d'essais CPT et pressiométriques

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