Search

The problem of localizing small (relative to wavelength) scatterers by diffractions to enhance their use in identifying small-scale details in a seismic image is extremely important in shallow exploration to identify interesting features such as fractures, caves, and faults. The conventional approach based on seismic reflection is limited in resolution by the Rayleigh criterion. In certain acquisition geometries, such as crosswell surveys aimed at obtaining high-resolution signals, the availability of suitable data sets for effective migration depends on the spatial extent of the available source and receiver data intervals. With the aim of overcoming the resolution limits of seismic reflection, we study the detectability, response, and location of meter- and possibly submeter-dimension carbonate concretions (septaria) in the Boom Clay Formation (potential host rocks for radioactive waste disposal) by diffraction analysis of high-frequency signals. We investigate diffraction wavefields by signal separation, focusing, and high-resolution coherency analysis using the multiple signal classification method and semblance. The investigation is performed for two different surveys in Belgium, a shallow and high-resolution reverse vertical seismic profile (RVSP) and a near-offset crosswell application at Kruibeke and ON-MOL-2 sites, respectively. The data analysis is supported by synthetic wavefield modeling. The multioffset RVSP provides the appropriate geometry to observe and investigate the septaria diffractions from depth and the surface. The crosswell approach, calibrated using synthetic data in the analysis of wavefield patterns in 2D, indicates promising imaging results with field data of a selected diffraction zone in the interwell area.

Faults may impact regional groundwater flow and transport, so it is important to include them during aquifer-system conceptualization and while constructing groundwater flow models. For the Neogene aquifer in Flanders (Belgium), three-dimensional groundwater-flow and solute-transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay Formation as a potential host for geological disposal of radioactive waste. The model outcomes are subject to uncertainties as they are typically constrained only by hydraulic heads, and their current conceptualization does not differentiate the fault zones from the undisturbed hydrostratigraphic formations. A groundwater flow model has been developed using MODFLOW-2005 to investigate how groundwater flow in the sedimentary Neogene aquifer may be disturbed by the Rauw Fault—a 55-km-long normal fault—across the Nete catchment. The observed hydraulic gradient across the fault zone appears significant, with head differences of 1.5–2.0 m over a horizontal distance of 60 m. A simulated hydraulic-head difference of 2.4 m was achieved largely corresponding to the observed behavior. The Neogene aquifer, within the Nete catchment, seems to be composed of several local flow systems and potentially with a deeper more semiregional/intermediate flow system. Testing different fault configurations shows the impact on the local/semiregional flow system, with pronounced effects in the fault’s vicinity, and extending or narrowing the flow systems further away. These results demonstrate the importance of considering faults, or any other hydrogeological subsurface barrier/conduit, and suggests they should be accounted for in the general practice of subsurface activity impact assessment.

Heat is a naturally occurring, widespread groundwater tracer that can be used to identify flow patterns in groundwater systems. Temperature measurements, being relatively inexpensive and effortless to gather, represent a valuable source of information which can be exploited to reduce uncertainties on groundwater flow, and, for example, support performance assessment studies on waste disposal sites. In a lowland setting, however, hydraulic gradients are typically small, and whether temperature measurements can be used to inform us about catchment-scale groundwater flow remains an open question. For the Neogene Aquifer in Flanders, groundwater flow and solute transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay formation as a potential host rock for geological disposal of radioactive waste. However, the simulated fluxes by these models are still subject to large uncertainties as they are typically constrained by hydraulic heads only. In the current study, we use a state-of-the-art 3D steady-state groundwater flow model, calibrated against hydraulic head measurements, to build a 3D transient heat transport model, for assessing the use of heat as an additional state variable, in a lowland setting and at the catchment scale. We therefore use temperature–depth (TD) profiles as additional state variable observations for inverse conditioning. Furthermore, a Holocene paleo-temperature time curve was constructed based on paleo-temperature reconstructions in Europe from several sources in combination with land surface temperature (LST) remotely sensed monthly data from 2001 to 2019 (retrieved from NASA's Moderate Resolution Imaging Spectroradiometer, MODIS). The aim of the research is to understand the mechanisms of heat transport and to characterize the temperature distribution and dynamics in the Neogene Aquifer. The simulation results clearly underline advection/convection and conduction as the major heat transport mechanisms, with a reduced role of advection/convection in zones where flux magnitudes are low, which suggests that temperature is also a useful indicator in a lowland setting. Furthermore, the performed scenarios highlight the important roles of (i) surface hydrological features and withdrawals driving local groundwater flow systems and (ii) the inclusion of subsurface features like faults in the conceptualization and development of hydrogeological investigations. These findings serve as a proxy of the influence of advective transport and barrier/conduit role of faults, particularly for the Rauw fault in this case, and suggest that solutes released from the Boom Clay might be affected in similar ways.

Environmental tracers are naturally occurring widespread substances in a hydrogeological system that can be used to identify flow pathways, travel times, groundwater age, and recharge rates. However, these are not typically included during the numerical model inversion process. Recent work has broadened their use in a quantitative way by incorporating them in formal solutions of the inverse problem to estimate hydraulic properties and groundwater fluxes. This is commonly done with numerical codes that at least enable one-way coupling of the different processes, i.e., groundwater flow and solute-transport. Helium-4, carbon-14 and temperature-depth profile measurements represent a valuable source of information which can be exploited to support performance assessment studies. For the Neogene aquifer in Flanders, groundwater flow and solute transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay Formation as potential host for geological disposal of radioactive waste. However, the simulated fluxes by these models are still subject to large uncertainties, as they are typically constrained by hydraulic heads only. While the evaluation of candidate host formations continues, the use of age tracers (e.g. 4He) as additional (unconventional) state variable for inverse conditioning is being explored. Current methodological developments to integrate such additional unconventional observations will allow i) to test our current understanding and corresponding models of the system, and ii) to potentially decrease the uncertainties associated with model outcomes by a joint inversion approach. From previous campaigns, a total of 18 4Herad observations have been collected at selected sites across the Nete catchment. Furthermore, the accumulation of 4Herad by in situ production and crustal flux is included in the inversion of the 4He-transport model, where the uncertainty of groundwater flow and transport model parameters is evaluated. Additionally, a Latin hypercube sampling (LHS) design is done with parameters drawn from prior distributions. The corresponding simulation results are used to construct a neural network surrogate model to be used for uncertainty quantification using Bayesian inference. Here, we will present the first results and interpretations of Helium-4 as potential additional state variable for inverse conditioning, and constraining groundwater flow and solute transport models at the catchment scale.

Heat is a naturally occurring widespread groundwater tracer that can be used to identify flow patterns in groundwater systems. Temperature measurements, being relatively inexpensive and effortless to gather, represent a valuable source of information which can be exploited to reduce uncertainties on groundwater flow, and e.g. support performance assessment studies on waste disposal sites. In a lowland setting, however, hydraulic gradients are typically small, and whether temperature measurements can be used to inform us about catchment-scale groundwater flow remains an open question. For the Neogene aquifer in Flanders, groundwater flow and solute transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay Formation as potential host rock for geological disposal of radioactive waste. However, the simulated fluxes by these models are still subject to large uncertainties, as they are typically constrained by hydraulic heads only. In the current study we use a state-of-the-art 3D steady-state groundwater flow model, calibrated against hydraulic head measurements, to build a 3D transient heat-transport model, for assessing the use of heat as an additional state variable, in a lowland setting, at the catchment scale. We therefore use temperature-depth (TD) profiles as additional state variable observations for inverse conditioning. Furthermore, a Holocene paleo-temperature time curve was constructed based on paleo-temperature reconstructions in Europe from several sources in combination with land-surface temperature (LST) imagery remote sensing monthly data from 2001 to 2019 (retrieved from NASA’s MODIS). The aim of the research is to understand the mechanisms of heat transport and to characterize the temperature distribution and dynamics in the Neogene aquifer. The simulation results clearly underline advection/convection and conduction as the major heat transport mechanisms, with a reduced role of advection/convection in zones where flux magnitudes are low, which suggests temperature is a useful indicator also in a lowland setting. Furthermore, performed scenarios highlight the important roles of i) surface hydrological features and withdrawals driving local groundwater flow systems, and ii) the inclusion of subsurface features like faults in the conceptualization and development of hydrogeological investigations. These findings serve as a proxy of the influence of advective transport and barrier/conduit role of faults, particularly the Rauw Fault in this case, and suggest that solutes released from the Boom Clay might be affected in similar ways.

Faults play an important role in flow and transport in regional groundwater systems. The inclusion of faults during the conceptualization of regional groundwater systems and their incorporation during the construction of groundwater models is crucial, particularly during performance assessments of radioactive waste repositories as well as risk assessment for other deep subsurface activities. Faults can act as: i) barriers slowing down groundwater flow, ii) conduits speeding up groundwater flow, or iii) a combination of both. Determining flow and transport behaviors across these structures is difficult since they are rarely exposed on the surface and their hydraulic behavior vary spatially. Environmental tracers may provide valuable information potentially useful to determine flow pathways, travel times, and groundwater age. If these latter are affected by the presence of fault zones, and they can yield important information for the parameterization of faults in groundwater models. For the Neogene aquifer in Flanders, groundwater flow and solute transport models have been developed in the framework of safety and feasibility studies for the underlying Boom Clay Formation as potential host rock for geological disposal of radioactive waste. However, the simulated fluxes and transport parameters of these models are still subject to large uncertainties, as they are typically constrained by hydraulic heads only and their current conceptualization does not differentiate the fault zones from the undisturbed aquifer materials. This study investigates how groundwater flow and solute transport in the sedimentary Neogene aquifer are disturbed by the Rauw fault – a 55 km long normal fault – across the Nete catchment, in Belgium. To this end, we use a combination of hydraulic head observations and several environmental tracers: hydrochemical analyses, stable isotopes, carbon-14 (14C), helium-tritium (3He-3H), helium-4 (4He) and temperature-depth (TD) profiles. This will allow us to: i) test our current understanding of the system as well as the corresponding model performance, and ii) decrease the uncertainties on forward model outcomes for future scenarios and inverse models by including an advanced conceptualization. The Rauw fault has a displacement of >7 meters which increases with depth. The observed hydraulic gradient across the fault zone appears significant, with head differences of 1.8-2.0 meters over an horizontal distance of 60 meters. Two sampling campaigns have taken place, in 2016 and 2019, for collection of 3He-3H, 4He, 14C, and TD data at a total of 38 selected wells across the Nete river catchment. These will be further used as observations points for the transport modelling. Here, we will present the first results and interpretations of the gathered temperature and environmental tracer data in complementation with hydraulic head levels to evaluate the effects of the Rauw Fault on the hydrogeological system and the implications future conceptualization and numerical modelling.

Our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology. Here, we evaluate the co-seismic character and movement history of the Rauw fault in Belgium, which lacks geomorphological expression and historical/present seismicity. This 55-km-long normal fault, with known Neogene and possibly Early Pleistocene activity, is the largest offset fault west of the active Roer Valley Graben. Its trace was identified in the shallow subsurface based on high resolution geophysics. All the layers within the Late Pliocene Mol Formation (3.6 to 2.59 Ma) are displaced 7 m vertically, without growth faulting, but deeper deposits show increasing offset. A paleoseismic trench study revealed cryoturbated, but unfaulted, late glacial coversands overlying faulted layers of Mol Formation. In-between those deposits, the fault tip was eroded, along with evidence for individual displacement events. Fragmented clay gouge observed in a micromorphology sample of the main fault evidences co-seismic faulting, as opposed to fault creep. Based on optical and electron spin resonance dating and trench stratigraphy, the 7 m combined displacement is bracketed to have occurred between 2.59 Ma and 45 ka. The regional presence of the Sterksel Formation alluvial terrace deposits, limited to the hanging wall of the Rauw fault, indicates a deflection of the Meuse/Rhine confluence (1.0 to 0.5 Ma) by the fault's activity, suggesting that most of the offset occurred prior to/at this time interval. In the trench, Sterksel Formation is eroded but reworked gravel testifies for its former presence. Hence, the Rauw fault appears as typical of plate interior context, with an episodic seismic activity concentrated between 1.0 and 0.5 Ma or at least between 2.59 Ma to 45 ka, possibly related to activity variations in the adjacent, continuously active Roer Valley Graben.

The chronostratigraphy of the typical quartz-rich white sands that are intensively quarried in the Campine area, northeastern Belgium, is poorly constrained. In the absence of biostratigraphical data, the age of the deposits, traditionally assigned to the Mol Formation, is thought to be late Pliocene based on sequence stratigraphical correlations (ca. 2.6–3.6 Ma). In an attempt to verify this age, we used a multi-dating method approach on two carefully selected samples in a palaeoseismological trench where the sediment was found to be vertically displaced by the Rauw fault. Three dating methods were used: electron spin resonance (ESR) dating, optically stimulated luminescence (OSL) dating and cosmogenic radionuclide (CRN) dating. In all three cases quartz was found to be a suitable dating material in terms of material properties. However, the ESR dating results based on Ti, Ti–Li and Al centres show strong internal inconsistencies, which can be explained by incomplete bleaching. As such, the youngest ESR ages obtained (ca. 5 Ma) are regarded as an absolute maximum age. In contrast, the OSL ages of ca. 1.5 Ma seem to underestimate the sequence stratigraphical age. The surface exposure CRN dating method using Bayesian inversion suggests that a palaeosurface developed around 1.55 ± 0.80 Ma, and eroded at a rate of ca. 15 m/Ma. Erosion probably accelerated after ca. 0.5–1 Ma and posterior to the last major movement along the Rauw fault.

1. Introduction This paper deals with the Kasterlee Formation in the Belgian Campine area (Antwerp and Limburg) and the transition from the Kasterlee Formation to the underlying Diest Formation and the overlying Mol Formation. Like many lithostratigraphic units in Belgium also the Kasterlee Formation has a stratigraphic precursor name ‘Casterlien’, already introduced in 1882 by Dumont. Its position with respect to over- and underlying strata has been a subject of debate in the stratigraphic literature (Tavernier, 1954; Laga & Louwye, 2006). The definition of the Kasterlee Formation presently described in the lithostratigraphy inventory of the National Commission for Stratigraphy Belgium (NCS) (https://ncs.naturalsciences.be/paleogene-neogene/25-kasterlee-formation-kl), follows the lithostratigraphy review by Laga et al. (2001) which is honouring the principles and the discussions about this unit by earlier authors such as Gulinck (1963, p. 33). The stratotype of the Kasterlee Formation is the hilly area on the right bank of the Kleine Nete valley ending in the east at the village of Kasterlee (the Lichtaart-Kasterlee hill ridge on Fig. 1). According to Laga et al. (2001) the Kasterlee Formation consists of grey micaceous sand without fossils, slightly glauconiferous with lenses of micaceous clay and micaceous fine sand at the base, often very glauconitic, burrowed and mottled. This description however is general and hardly allows a clear distinction from other lithostratigrap

National audience; Le web des documents et le web des données liées utilisent tous les deux les URL pour identifier les ressources et le protocole HTTP pour les échanger. Les navigateurs web actuels sont limités à l'affichage des documents HTML et, nativement, ils ne permettent pas l'affichage de données RDF. Nous proposons d'étendre les fonctionnalités des navigateurs pour parcourir le web dans son intégralité de la manière la plus intuitive possible, c'est-à-dire en suivant les liens entre ressources sans que leur format constitue un obstacle. Pour y parvenir, nous proposons une extension de navigateur permettant de visualiser les res-sources RDF et de naviguer sur le Web en passant d'une ressource HTML à une ressource RDF de manière transparente.

International audience; Building a complex system requires the collaboration of different stakeholders. They work together to model the system keeping in mind the requirements described in specification documents. This complexity induces a large volume of requirements and models, i.e., artefacts that will be subject to frequent changes during the project lifetime. Since the artefacts are correlated with each other's, each change has to be rigorously propagated. Identifying traceability links between system's artefacts is then a critical step to reach this goal. In Information Retrieval domain, many approaches have been already proposed to cope with traceability issues. Their main drawback is they introduce an important amount of false positive links making the traceability links validation phase time consuming and error-prone. In this paper, we propose an approach that identifies traceability links with a reduced amount of false positive links ranging from 20% to 30% while raising the amount of true links identified up to 70%. The approach consists of three main steps: 1) we measure syntactical and semantic similarities between pairs of artefacts by combining the use of four major Information Retrieval techniques; 2) using these similarity measures, we identify the most likely true and false links and we build the so called training data set; 3) this training data set and the four IR techniques are used as input of a predictive model in order to classify between true and false links leading ultimately to a reduced amount of false positives. The output is given in the form of a confidence measure that will help the modeller validating the traceability links. We evaluated our approach using four well-known public case studies. Each one comes with a clear identification of true traceability links which allowed us to compare with the outcome of our approach and validate its effectiveness.

In order to protect man and the environment, long-lasting, passive solutions are needed for the different categories of radioactive waste. In Belgium, three main categories of conditioned radioactive waste (termed A, B and C) are defined by radiological and thermal power criteria. It is expected that Category A waste – low and intermediate level short-lived waste – will be disposed in a near-surface facility, whereas Category B and C wastes – high-level and other long-lived radioactive waste – will be disposed in a deep geological repository. In both cases, the long-term safety of a given disposal facility is evaluated. Different scenarios and assessment cases are developed illustrating the range of possibilities for the evolution and performance of a disposal system without trying to predict its precise behaviour. Within these scenarios, the evolution of the climate will play a major role as the time scales of the evaluation and long term climate evolution overlap. In case of a near-surface facility (Category A waste), ONDRAF/NIRAS is considering the conclusions of the IPCC, demonstrating that a global warming is nearly unavoidable. The consequences of such a global warming and the longer term evolutions on the evolution of the near-surface facility are considered. In case of a geological repository, in which much longer time frames are considered, even larger uncertainties exist in the various climate models. Therefore, the robustness of the geological disposal system towards the possible results of a spectrum of potential climate changes and their time of occurrence will be evaluated. The results of climate modelling and knowledge of past climate changes will merely be used as guidance of the extremes of climate changes to be considered and their consequences.

The Boom Clay Formation of early Oligocene age, which occurs underground in northern Belgium, has been studied intensively for decades as a potential host rock for the disposal of nuclear waste. The goal of the present study is to determine a reference composition for the Boom Clay using both literature methods and methods developed during this work. The study was carried out on 20 samples, representative of the lithological variability of the formation. The bulk-rock composition was obtained by X-ray diffraction using a combined full-pattern summation and singlepeak quantification method. Siliciclastics vary from 27 to 72 wt.%, clay minerals with 25–71 wt.% micas, 0–4 wt.% carbonates, 2–4 wt.% accessory minerals (mainly pyrite and anatase) and 0.5–3.5 wt.% organic matter. This bulk-rock composition was validated independently by majorelement chemical analysis. The detailed composition of the clay-sized fraction was determined by modelling of the oriented X-ray diffraction patterns, using a larger sigma star (σ*) value for discrete smectite than for the other clay minerals. The

International audience; The design of nowadays complex systems requires a collaboration between a diversity of stakeholders: from domain experts to customers. For a collaboration to be efficient, the relevant information have to reach the right stakeholder at the right time in a format that is understandable to him/her. We propose a formal framework to integrate the meaning projected by stakeholders onto their data (the denotation), so that it can be unambiguously used by others. An implementation of this framework, relying on the existing language xOWL (extension of OWL2 with behavioral constructs), is then provided to perform the semantic integration of the captured denotations in an MBSE approach.

Today, we live in a society where time and space have been shortened by the introduction of digital technologies. This situation puts a lot of pressure on the market and companies unable to adapt are doomed to extinction. Collaboration is needed. Although the Systems Engineering approach brings many benefits to manage risks and to improve the quality, cost and delay of deliveries; we argue in this paper that we are missing today adapted methods and tools in the Model-Based System Engineering to support this change of paradigm. Based on use cases' observations, 5 collaborative systems engineering challenges are raised to position 2 research tracks.

Conference of 19th IFAC World Congress on International Federation of Automatic Control, IFAC 2014 ; Conference Date: 24 August 2014 Through 29 August 2014; International audience; In a Model-Driven Engineering methodology, the design phase of a product involves the creation of models in multiple domains. A current industrial issue is the integration of domain-specific models in order to homogeneously design the product from the different perspectives. For example, testing a product (e.g. a plane) based on its model is easier and cheaper, but requires the domain-specific representations to be integrated. This paper proposes to solve this integration issue through the use of OWL ontologies. It emphasizes the importance of taking care of the behavioral semantics of the domain-specific models and provides a solution based on the xOWL language, used for the expression of behaviors within ontologies. This paper is supported by a case study, extracted from the industry, about the multiple domains of expertise involved in the design of an aircraft's cockpit.

This chapter follows the development process of a cyber-physical system in the railway industry. It starts from the scenario of passengers getting on and off an autonomous train and explores the engineering steps from the identification of the user needs down to the system design and implementation. The chapter emphasizes the iterative and collaborative nature of the engineering process with a special care for the continuous verification of engineering choices. Moreover, it studies how engineering data are shared across disciplines, as this is a key element supporting continuous verification.

The rate at which low-lying sandy areas in temperate regions, such as the Campine Plateau (NE Belgium), have been eroding during the Quaternary is a matter of debate. Current knowledge on the average pace of landscape evolution in the Campine area is largely based on geological inferences and modern analogies. We performed a Bayesian inversion of an in situ-produced 10Be concentration depth profile to infer the average long-term erosion rate together with two other parameters: the surface exposure age and the inherited 10Be concentration. Compared to the latest advances in probabilistic inversion of cosmogenic radionuclide (CRN) data, our approach has the following two innovative components: it (1) uses Markov chain Monte Carlo (MCMC) sampling and (2) accounts (under certain assumptions) for the contribution of model errors to posterior uncertainty. To investigate to what extent our approach differs from the state of the art in practice, a comparison against the Bayesian inversion method implemented in the CRONUScalc program is made. Both approaches identify similar maximum a posteriori (MAP) parameter values, but posterior parameter and predictive uncertainty derived using the method taken in CRONUScalc is moderately underestimated. A simple way for producing more consistent uncertainty estimates with the CRONUScalc-like method in the presence of model errors is therefore suggested. Our inferred erosion rate of 39 ± 8. 9 mm kyr−1 (1σ) is relatively large in comparison with landforms that erode under comparable (paleo-)climates elsewhere in the world. We evaluate this value in the light of the erodibility of the substrate and sudden base level lowering during the Middle Pleistocene. A denser sampling scheme of a two-nuclide concentration depth profile would allow for better inferred erosion rate resolution, and including more uncertain parameters in the MCMC inversion., Earth Surface Dynamics, 5 (2), ISSN:2196-632X, ISSN:2196-6311

We have compiled a dataset containing information on patterns of burial and erosion that occurred during the last ca. 30 Ma in the Campine area, north-eastern Belgium. This area coincides with the occurrence of the Rupelian Boom Clay which is considered as one of the potential host formations for radwaste disposal. Patterns and estimates of erosion and sedimentation, based on geological and geomorphological data, from several locations within the Boom Clay outcrop and subcrop zone, show increasing burial in northern and north-eastern direction over the last 30 Ma. More southern areas have experienced erosion and denudation during some geological stages, usually in the order of several 10 m, up to 100 m at most at two discrete locations. During the Quaternary, erosion is a widespread phenomenon in the Campine area, except in the Roer Valley Graben. The obtained estimates of erosion and burial are compared and discussed in the context of the overall geodynamic evolution of north-western Europe.

The Boom Clay is currently investigated as potential host formation for the deep disposal of high-level and/or long-lived radioactive waste in Belgium. As such, the formation is expected to play a role of natural barrier, to slow the migration of radionuclides towards the biosphere for a sufficiently long time when the man-made barriers are no longer effective. In this context, the Boom Clay aquitard requires to be precisely characterized in terms of hydrogeological parameters, to confirm its role of geological barrier between its surrounding aquifers. Therefore, hydraulic conductivity and migration parameters have been intensively measured over the years in a few boreholes in Belgium; the latter are mainly located in the Mol-Dessel area, assuming historically a good lateral continuity of the geology. Combining these measurements with more densely acquired geophysical information allows quantifying their spatial variability and consolidating the continuity assumption. From a methodological point of view, the modeling of hydrogeological parameters requires to solve several issues. First, it is required to find a consistent geo-reference coordinate system allowing to laterally correlate thin observations derived from boreholes separated by several tens of kilometers. Then, in order to provide a reliable 3D model, it is compulsory to integrate the correlation between the scarcely sampled target parameters (core measurements) and numerous geophysical logs (gamma ray, resistivity). Geostatistics provides a suitable framework to analyze and solve these issues. Finally, a 3D model of the target parameters is proposed, together with an uncertainty envelope. This uncertainty quantification is of significant added value to assess the efficiency of the geological barrier. Besides the actual modeling of target parameters, the paper also presents sampling recommendations for forthcoming boreholes.

The rate at which low-lying sandy areas in temperate regions, such as the Campine area (NE Belgium), have been eroding during the Quaternary is a matter of debate. Current knowledge on the average pace of landscape evolution in the Campine area is largely based on geological inferences and modern analogies. We applied Bayesian inversion to an in-situ produced 10Be concentration depth profile in fluvial sand, sampled on top of the Campine Plateau, and inferred the average long-term erosion rate together with three other parameters, i.e., the surface exposure age, inherited 10Be concentration and sediment bulk density. The inferred erosion rate of 44 ± 9 mm/kyr (1σ) is relatively large in comparison with landforms that erode under comparable (palaeo-)climates elsewhere in the world. We evaluate this value in the light of the erodibility of the substrate and sudden base level lowering during the Middle Pleistocene. A denser sampling scheme of a two-nuclide concentration depth profile would allow to include more parameters in the model inversion and further reduce their uncertainty.

Thin sections of the plastic Ieper Group and Boom Formation clay have shown a marked heterogeneity due to layering, erosion, bioturbation and pyrite distribution. In the most clay-enriched samples, compartments delineated by primary thin fissures are present and associated small drag lines indicate small displacement. Fissures and drag lines are impregnated with early pyrite pointing to permeable pathways.

Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl(-), Br(-)), water isotopes (delta(18)O, delta(2)H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in Mazurek et al. (2009). Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the entire data set. In essentially all cases, the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles. Transport by advection has a negligible influence on the observed profiles at most sites, as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data. The advantages and disadvantages of different conservative tracers are also assessed. The anion Cl(-) is well suited as a natural tracer in aquitards, because its concentration varies considerably in environmental waters. It can easily be measured, although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue. The stable water isotopes are also well suited, but they are more difficult to measure and their values generally exhibit a smaller relative range of variation. Chlorine isotopes (delta(37)Cl) and He are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence. It is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion, leading to relatively sharp changes of boundary conditions, can be considered as a pre-requisite to obtain well-interpretable tracer signatures. On the other hand, gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation.

Fractures, from vertical joints to micro-scale slickensides, are common in many muds and mudstones. Their origin and formation mechanism remains enigmatic because of the rock–soil transitional behaviour of argillaceous sediments. However, they can have an important impact on the fluid-flow properties and mechanical strength of the rock. The nature of small-scale fractures studied in the field and in the laboratory is discussed using fabric, strain and paleostress analyses, for the case of Oligocene Boom Clay (Belgium). Non-dilatant ductile and dilatant brittle structures develop successively in the stress path of the deforming mud, which remains close to its critical stress state due to its low strength. The transition between the failure modes depends on the mean effective stress, the water content, the amount of strain and the burial-uplift history. The specific stress path initially follows a K 0 path that is left when differential stress increases, due to both uplift and compaction-induced endogenous forces, reflected by a decrease in effective confining pressure prior to failure, and far-field tectonic forces, reflected by the distinct and regular orientation of fractures. The related deformation is ductile, causing distributed micro-shear bands, up to the dilatancy boundary, beyond which extensional fractures develop.

Several transport parameters (as hydraulic conductivity K, apparent diffusion coefficient Dp and diffusion accessible porosity η of HTO and iodide) have been intensively measured in the laboratory on high-quality cores taken at the Mol-1 borehole of the Mol site, in Belgium. The borehole was cored in 1997 from about 145 to 325 m depth, including the whole thickness of the Boom Formation, a Tertiary clay situated between 186 and 288 m depth (ground level), and part of the surrounding layers. The hydraulic conductivity measurements confirm the low permeability of the Boom Clay. An upper 90-m-thick clay layer within this formation can be considered as homogeneous with respect to the hydraulic conductivity. The vertical hydraulic conductivity Kv (i.e. K perpendicular to the bedding) is in the order of magnitude of 10−12 m s−1 and the average is 2.3×10−12 m s−1. This layer comprises from top to bottom the “Transition Zone”, the Putte Member, the Terhagen Member and the top of the Belsele-Waas Member of the Boom Formation. The 12 m at the base of the Formation, which corresponds to the lower part of the Belsele-Waas Member is characterised by larger Kv values (ranging between 10−11 and 9×10−11 m s−1). The same thick clay layer can also be considered as homogeneous, regarding the values of the apparent diffusion coefficient and the diffusion accessible porosity η of tritiated water (HTO) and iodide. The average value of the diffusion accessible porosity is 0.37±0.03 for HTO and 0.16±0.02 for iodide. The apparent diffusion coefficient varies from 1.1×10−10 to 5.5×10−10 m2 s−1 for HTO and from 9.1×10−11 to 5.2×10−10 m2 s−1 for iodide.

Recent Underground Research Facility (URF) gallery excavation works in the Boom Clay at 224 m below the surface revealed intense fracturing of this weak claystone. Large fault planes (meter-scale) and joints were observed during tunnelling and found to belong to the excavation-disturbed zone (EDZ). Samples taken from the new gallery have been investigated using scanning electron microscope (SEM) imagery and microstructural analysis. This revealed a brittle–ductile transitional behaviour of the mudstone sediment regarding deformation, implying dilatant shear and hybrid fractures in high strain zones and ductile, compacted plastic shear bands in the lower strain zones, following an elasto-plastic constitutive model. Microfabric analysis contributed in this way to a better understanding of clay behaviour and effective fracturing. This information is primordial for understanding the rheology of the clay and assessing the influence of fracturing on permeability, critical issues in radioactive waste management.

Permian to Lower Jurassic strata, deposited between Variscan and Cimmerian deformation phases, subcrop in the northeastern Campine basin and Roer Valley Graben (NE Belgium). Total preserved thickness attains 550 m (of which 520 m drilled) in the Campine basin and ca. 1500 m (of which 1250 m drilled) in the Roer Valley Graben. Discovery of these concealed deposits is due to coal exploration of the Campine basin; further interest is linked to their potential for energy production or storage. Permo-Triassic sediments displaying Germanic facies were deposited on the southern margin of the Southern Permian Basin; Pangaea break-up associated with opening of the North Atlantic created conditions for deposition of the fully marine Jurassic sediments. Therefore, the stratigraphical succession in northeastern Belgium is closely related to the Dutch stratigraphical nomenclature.

International audience; An experimental characterisation on Ypresian clays that are considered as one of the potential geological host formations for the radioactive waste disposal in Belgium has been carried out. Physical, microstructural, hydraulic and mechanical properties were investigated on the samples taken from a cored borehole at Kallo in the Northern Belgium at 290-400 m depth. Identification tests, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and oedometer tests were performed. The results obtained showed that Ypresian clays are highly plastic (large values of consistence limits, specific surface, blue ethylene value) and of relatively low density, in relation to their high swelling clay content. In addition, their physical and mineralogical properties present significant variations over depth. Two microstructural arrangements, matrix-type and aggregate-type respectively for the depths with higher and lower swelling content, were identified. The former exhibits bi-modal porosity while the latter shows a common deep sediment mono-modal porosity but with a larger dominant pore size. The permeability of the clays with matrix-type microstructure is significantly lower than that with aggregate-type despite their higher void ratio. Moreover, these microstructural features result in the initial unsaturated state of Ypresian clays sample. Typical hysteretic unloading-reloading loops are identified on both low- and high-pressure oedometer tests that can be explained by a microstructure-based swelling stress concept. The variation of this swelling stress with the corresponding initial void ratio over depth perfectly reflects the physical variations and is consistent with that of swelling stress determined from common swelling tests. The yield stress ratios are slightly higher than the over-consolidation ratio, suggesting negligible effects of diagenesis, cambering and valley bulging etc. The variations of compression index, compression and swelling slopes are consistent with the physical and microstructural variations.

Nowadays, enterprises such as the European Aeronautic Defense and Space Company (EADS) span the development of their products across multiple countries with different languages. At the same time, the development of the products involves experts from multiple fields of expertise. For example, thermal and electrical engineers need to collaborate for the design of the same aircraft in the aeronautics industry. Yet they sometimes speak different languages (French and German). The vocabulary in the aeronautic is very precise and requires a level of understanding best achieved by the experts in their native language. Hence, they need a system supporting their collaborative design activities bridging the gaps between the different fields of expertise, as well as languages. In this paper, we demonstrate such a system, which is validated by an implementation and its application on a use case coming from the aeronautic industry.

International audience; Domain-Specific Modeling Languages (DSMLs) enable domain experts to represent their knowledge through their own domain-specific notations. The Model-Driven Engineering (MDE) community proposes a metamodel-driven approach for the production of tools implementing said DSMLs, i.e. one has to first devise the metamodel of a domain and then its notation. In an industrial context, the adoption by domain experts of modeling tools is a challenging issue. EADS as a major aircraft manufacturer faces this problem with experts from multiple fields. In this paper we argue that a notation-based approach, i.e. first designing the notation and then automatically generating the domain metamodel, would yield notations closer to experts' expectations; thus maximizing the adoption rate of the modeling tools. In order to test this hypothesis, we devised an empirical study comparing such a notation-driven approach to the metamodel-driven approach. We present in this paper the results and conclusions of this study.

Boom Clay and Ypresian Clays have been considered as potential geological host formations for radioactive waste disposal in Belgium. Considering the significant differences in pore water chemical composition between several sites involving these two formations as well as the possible evolution of the chemical composition during the large lifespan of a radioactive waste disposal, it appeared important to investigate the effects of pore water chemical composition on the hydro-mechanical behaviors of these two potential host formations. In this study, these effects were investigated by carrying out specific œdometer tests. Different compositions were considered for this purpose: distilled water, synthetic site water, and Sodium Chloride solutions at concentrations of 15 and 30 g/L. Clear effects of pore water chemical composition on the hydro-mechanical behavior were observed: increasing pore water salt concentration gave rise to (i) increase of œdometric modulus E œd , permeability K and consolidation coefficient C v ; and (ii) decrease of compression slope c ′ c , swelling slope c ′ s and secondary compression coefficient C αe , which is in agreement with the diffuse double layer theory and the clay particle aggregation as identified by microstructural analyses. Furthermore, the pore water chemical composition effects were found to be mineralogy, stress state and salt concentration dependent: (i) Ypresian Clays with higher smectite content showed clearer chemical effect on the coefficient of consolidation C v ; (ii) the chemical effects on compressibility and swelling capacity parameters were found to be attenuated with increasing vertical stress; and (iii) the increase of chemical effect with increasing pore water salinity was limited to a certain salt concentration. The competition between the physico-chemical and mechanical effects was identified: the pore water chemical composition effect is clear only in the low-stress range where the hydro-mechanical behavior is dominated by the physico-chemical effect.

International audience; This paper deals with the problem, coming from an industrial context, of ontology transformations. EADS, as a major aircraft manufacturer faces the problem of integrating works of experts from different domains using different notations. Addressing this Domain-Specific Language (DSL) problem, we previously developed a solution based on OWL2 ontologies for the integration of multiple domains at the abstract syntax level. Our next step is then the production of visual concrete syntaxes from this abstract syntax, for each domain. Considering this problem as a transformation issue, we raise the challenge of ontology transformations. We provide an OWL2-based rule language for the expression of such transformations. Validating this approach, our rule language has been implemented in a rule and transformation engine and tested on applications coming from the industry.

International audience; Boom clay has been selected as a potential host rock formation for the geological disposal of radioactive waste in Belgium. In the present work, the hydro-mechanical behaviour of Boom clay samples from the borehole Essen-1 at a depth of 220 - 260 m and from HADES that is the underground rock laboratory at Mol in Belgium, at 223-m depth was investigated in the laboratory by performing low pressure oedometer tests (vertical effective stress ranging from 0.05 to 3.2 MPa), high pressure oedometer tests (vertical effective stress ranging from 0.125 to 32 MPa), isotropic consolidation tests (confining effective stress ranging from the in-situ stress to 20 MPa) and triaxial shear tests. It has been observed that the mineralogy, geotechnical properties and hydro-mechanical behaviour of Boom clay from Essen at 227-m, 240-m and 248-m depths are similar to that of Boom clay from Mol. As in the case of Boom clay at Mol, the failure envelope of Boom clay at Essen in the p'-q plane is not linear. The slope of the portion beyond the pre-consolidation stress of Boom clay from Essen is almost the same as that from Mol, suggesting a similar internal friction angle of about 13°. The compression curves (void index Iv versus logarithm of vertical stress) beyond the pre-consolidation stress are the same for both samples from Mol and Essen, and situated between the intrinsic compression line (ICL) and the sedimentation compression line (SCL). The yield stress determined from oedometer tests seems to be stress-path dependent and lower than the pre-consolidation stress. Thus determining the over-consolidation ratio (OCR) using the yield stress value would lead to an incorrect estimate. From a practical point view, the laboratory test results from Essen and their comparison with those from Mol provide important information regarding the transferability of knowledge on Boom clay at different sites, taking into account the fact that most investigations have been carried out on Boom clay at Mol.

In this paper, we first present an analysis of a multi-language application from a cross-cultural point of view. Then we analyze the specific activities of a multilingual collaborative design and the automatic translation system that it requires. We also propose an architecture of a design support system producing the UML design of applications and allowing a multilingual collaboration. We present the first results of an experiment with such a system.

Soft-sediment deformation involves complex interactions between discrete fracturing and diffuse bulk strain, described in terms of volume change and shear strain in a critical state mechanics framework. This study reports on a mesoscale normal fault zone, intraformational in Oligocene argillaceous sediments from the Boom Formation (Belgium), containing several metre-scale normal fault strands. They form either discrete fault planes or decimetre-wide shear zones with internal fabric. The faults have been subjected to microtectonic and petrophysical analysis. Small but significant changes occur in the porous network of the argillaceous matrix approaching a fault or shear zone, indicating compactional strain in both footwall and hanging wall. Internal compaction associated with faulting is put forward as a ductile–brittle feedback mechanism in the kinematics of intraformational fracture systems. Small differential stress induced by compaction and minor regional tectonic forces (differential uplift and tilt) and subsequent gravitational forces (downslope shear stress) induce small shear bands in nearly critically stressed weak mud. Shear banding is accompanied by layer-parallel shortening and bulk volume loss. This provides an additional extension of endogenous origin, accommodated by further deformation. This ductile–brittle feedback mechanism eventually leads to commonly observed intraformational collapse structures called polygonal fault systems.