References of "Charlier, Robert"
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See detailValidation of a new elastoplastic constitutive model dedicated to the cyclic behaviour of brittle rock materials
Cerfontaine, Benjamin ULg; Charlier, Robert ULg; Collin, Frédéric ULg et al

in Rock Mechanics & Rock Engineering (2017)

Old mines or caverns may be used as reservoirs for fuel/gas storage or in the context of large-scale energy storage. In the first case, oil or gas is stored on annual basis. In the second case pressure ... [more ▼]

Old mines or caverns may be used as reservoirs for fuel/gas storage or in the context of large-scale energy storage. In the first case, oil or gas is stored on annual basis. In the second case pressure due to water or compressed air varies on a daily basis or even faster. In both cases a cyclic loading on the cavern’s/mine’s walls must be considered for the design. The complexity of rockwork geometries or coupling with water flow requires finite element modelling and then a suitable constitutive law for the rock behaviour modelling. This paper presents and validates the formulation of a new constitutive law able to represent the inherently cyclic behaviour of rocks at low confinement. The main features of the behaviour evidenced by experiments in the literature depict a progressive degradation and strain of the material with the number of cycles. A constitutive law based on a boundary surface concept is developed. It represents the brittle failure of the material as well as its progressive degradation. Kinematic hardening of the yield surface allows the modelling of cycles. Isotropic softening on the cohesion variable leads to the progressive degradation of the rock strength. A limit surface is introduced and has a lower opening than the bounding surface. This surface describes the peak strength of the material andallows the modelling of a brittle behaviour. In addition a fatigue limit is introduced such that no cohesion degradation occurs if the stress state lies inside this surface. The model is validated against three different rock materials and types of experiments. Parameters of the constitutive laws are calibrated against uniaxial tests on Lorano marble, triaxial test on a sandstone and damage-controlled test on Lac du Bonnet granite. The model is shown to reproduce correctly experimental results, especially the evolution of strain with number of cycles. [less ▲]

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See detailDecoding the disciplines – A pilot study at the University of Liège (Belgium)
Verpoorten, Dominique ULg; Devyver, Julie ULg; Duchâteau, Dominique ULg et al

in Andersson, Roy; Martensson, Katarina; Roxa, Torgny (Eds.) Proceedings of the 2nd EuroSoTL Conference - Transforming patterns through the scholarship of teaching and learning (2017, June)

This paper reports on a first attempt to apply the two first stages of the “Decoding the disciplines” framework (Pace, 2017) at the University of Liège (Belgium). In this context, 7 professors volunteered ... [more ▼]

This paper reports on a first attempt to apply the two first stages of the “Decoding the disciplines” framework (Pace, 2017) at the University of Liège (Belgium). In this context, 7 professors volunteered to reflect, through a structured process, upon “bottlenecks” in their courses, with the help of IFRES’ (Institute for Training and Research in Higher Education) pedagogical advisers. This pilot delivered contrasted observations: while participants granted value to their exposure to this approach, especially in terms of enhanced awareness of possible discrepancies between what experts and newcomers in the field might consider as obvious, none of them activated the possibility offered to tackle the identified bottlenecks, according to the systematic approach (stages 3-7) suggested by the framework. The paper presents the pedagogical setting, analyses the interviews of participants and the outcomes of the project, outlines explanations for its results, and shares some lessons learnt. [less ▲]

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See detailA water retention model for compacted bentonites
Dieudonné, Anne-Catherine ULg; Della Vecchia, Gabriele; Charlier, Robert ULg

in Canadian Geotechnical Journal (2017)

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See detailNumerical simulation of a discontinuous gallery lining's behavior, and its interaction with rock
Salehnia, Fatemeh ULg; Sillen, Xavier; Li, XiangLing et al

in International Journal for Numerical and Analytical Methods in Geomechanics (2017)

Deep excavation in some geological media needs lining of the gallery. This could limit the extent of the so-called excavation damaged zone and the resulting convergence of the material due to tunneling ... [more ▼]

Deep excavation in some geological media needs lining of the gallery. This could limit the extent of the so-called excavation damaged zone and the resulting convergence of the material due to tunneling. Boom clay, the reference potential host rock in Belgium for disposal of high-level radioactive waste, is one of these media for which lining of the gallery walls is essential. A correct simulation of the lining behavior in the course of the excavation process, where the rock comes into contact with the lining, and in the long term, remains a significant challenge in analysis of the whole coupled phenomena of rock in interaction with the lining. This study aims to numerically model the lining behavior. The main objective is to develop a model that could realistically simulate the behavior of a discontinuous lining made of concrete segments. We propose to numerically analyze the response of the blocks in contact with each other and in interaction with rock, with the use of zero-thickness interface elements. To validate the developed model and a proposed approach, a particular analysis compares the obtained results with the available in situ measurements. This study then discusses the deficiency of the simplistic model that considers a continuous lining. In addition, regarding the contact mechanism on the interface between the rock and the lining, the obtained results demonstrate an interesting relation between the contact phenomena and the shear banding within the rock around the gallery. [less ▲]

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See detailEffect of undisturbed ground temperature on the design of closed-loop geothermal systems: A case study in a semi-urban environment
Radioti, Georgia ULg; Sartor, Kevin ULg; Charlier, Robert ULg et al

in Applied Energy (2017)

This paper presents temperature measurements in four Borehole Heat Exchangers (BHEs), equipped with fiber optics and located in a semi-urban environment (campus of the University of Liege, Belgium). A 3D ... [more ▼]

This paper presents temperature measurements in four Borehole Heat Exchangers (BHEs), equipped with fiber optics and located in a semi-urban environment (campus of the University of Liege, Belgium). A 3D numerical model is also presented to simulate the heat loss from the surrounding structures into the subsurface. The mean undisturbed ground temperature was estimated from data during the preliminary phase of a thermal response test (water circulation in the pipe loops), as well as from borehole logging measurements. The measurements during water circulation can significantly overestimate the ground temperature (up to 1.7 C in this case study) for high ambient air temperature during the test, resulting in an overestimation of the maximum extracted power and of the heat pump coefficient of performance (COP). To limit the error in the COP and the extracted power to less than 5%, the error in the undisturbed temperature estimation should not exceed ±1.5 °C and ±0.6 °C respectively. In urbanised areas, configurations of short BHEs (length < 40 m) could be economically advantageous (decreased installation and operation costs) compared to long BHEs, especially for temperature gradient lower than 0.05 °C/m. [less ▲]

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See detailShear banding simulation in clay rock around an underground opening, and its contact mechanism with the gallery’s lining
Charlier, Robert ULg; Salehnia, Fatemeh ULg

in Proc. 5th International conference on geotechnical engineering and soil mechanics (2016, November 15)

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

Diverse speeche and writing (2016)

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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 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 detailInteraction entre la zone endommagée autour d’un tunnel et son soutènement – Simulation numérique
Charlier, Robert ULg; Sillen, Xavier; Li, Xiangling et al

Conference (2016, May)

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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 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 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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See detailFormulation of a 1D finite element of heat exchanger for accurate modelling of the grouting behaviour: Application to cyclic thermal loading
Cerfontaine, Benjamin ULg; Radioti, Georgia ULg; Collin, Frédéric ULg et al

in Renewable Energy : An International Journal (2016), 96

This paper presents a comprehensive formulation of a finite element for the modelling of borehole heat exchangers. This work focuses on the accurate modelling of the grouting and the field of temperature ... [more ▼]

This paper presents a comprehensive formulation of a finite element for the modelling of borehole heat exchangers. This work focuses on the accurate modelling of the grouting and the field of temperature near a single borehole. Therefore the grouting of the BHE is explicitly modelled. The purpose of this work is to provide tools necessary to the further modelling of thermo-mechanical couplings. The finite element discretises the classical governing equation of advection-diffusion of heat within a 1D pipe connected to ground nodes. Petrov-Galerkin weighting functions are used to avoid numerical disturbances. The formulation is able to capture highly transient and steady-state phenomena. The proposed finite element is validated with respect to analytical solutions. An example consisting of a 100 m depth U-pipe is finally simulated. A first continuous heating simulation highlights the nonsymmetric distribution of temperature inside and near the borehole. An estimation of the error on the results as a function of the resolution parameters is also carried out. Finally simulations of cyclic thermal loading exhibit the need to take into account all daily variations if the grouting behaviour must be modelled. This is true especially in case of freeze-thaw damaging risk. [less ▲]

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See detailHeterogeneous bedrock investigation for a closed-loop geothermal system: A case study
Radioti, Georgia ULg; Delvoie, Simon ULg; Charlier, Robert ULg et al

in Geothermics (2016)

This paper investigates bedrock heterogeneity by applying three different geophysical approaches, in order to study the long-term behaviour and the interaction between closed-loop geothermal systems. The ... [more ▼]

This paper investigates bedrock heterogeneity by applying three different geophysical approaches, in order to study the long-term behaviour and the interaction between closed-loop geothermal systems. The investigated site consists of four boreholes equipped with geothermal pipes on the campus of University of Liege, Belgium. The first approach includes acoustic borehole imaging, gamma-ray logging and cuttings observation and results to a detailed fracture characterisation, rock identification and layer dip angle determination. The second approach consists of measuring the thermal conductivity of cuttings at the laboratory. Study of cuttings thermal conductivity measurements can contribute to bedrock heterogeneity knowledge concerning the transition of one formation to another and the layer dipping. The third approach is based on high-resolution temperature profiles, measured during the hardening of the grouting material and the recovery phase of a Distributed Thermal Response Test. Through this approach a correlation of the temperature profiles to the geological characteristics of the surrounding bedrock is identified. The analysis of this correlation can provide information on fractured zones, alternation of different rock types and layering dipping. This latter approach can be easily applied on closed-loop geothermal systems to characterise the bedrock and investigate its heterogeneity as well as contribute to the their long-term behaviour prediction and to the optimisation of their efficiency. [less ▲]

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