Clay Minerals Mapping from Imaging Spectroscopy

Mapping subsurface clay minerals is an important issue because they have particular behaviors in terms of mechanics and hydrology that directly affects assets laid at the surface such as buildings, houses, etc. They have a direct impact in ground stability due to their swelling capacities, constraining infiltration processes during flooding, especially when moisture is important. So detecting and characterizing clay mineral in soils serve urban planning issues and improve the risk reduction by predicting impacts of subsidence on houses and infrastructures. High-resolution clay maps are thus needed with accurate indications on mineral species and abundances. Clay minerals, known as phyllosilicates, are divided in three main species: smectite, illite, and kaolinite. The smectite group highly contributes to the swelling behavior of soils, and because geotechnical soil analyses are expensive and time-consuming, it is urgent to develop new approaches for mapping clays’ spatial distribution by using new technologies, e.g., ground spectrometer or remote hyperspectral cameras [0.4–2.5 μm]. These technics constitute efficient alternatives to conventional methods. We present in this chapter some recent results we got for characterizing clay species and their abundances from spectrometry, used either from a ground spectrometer or from hyperspectral cameras

Multiple Means to the Same End: The Genetic Basis of Acquired Stress Resistance in Yeast

In nature, stressful environments often occur in combination or close succession, and thus the ability to prepare for impending stress likely provides a significant fitness advantage. Organisms exposed to a mild dose of stress can become tolerant to what would otherwise be a lethal dose of subsequent stress; however, the mechanism of this acquired stress tolerance is poorly understood. To explore this, we exposed the yeast gene-deletion libraries, which interrogate all essential and non-essential genes, to successive stress treatments and identified genes necessary for acquiring subsequent stress resistance. Cells were exposed to one of three different mild stress pretreatments (salt, DTT, or heat shock) and then challenged with a severe dose of hydrogen peroxide (H2O2). Surprisingly, there was little overlap in the genes required for acquisition of H2O2 tolerance after different mild-stress pretreatments, revealing distinct mechanisms of surviving H2O2 in each case. Integrative network analysis of these results with respect to protein–protein interactions, synthetic–genetic interactions, and functional annotations identified many processes not previously linked to H2O2 tolerance. We tested and present several models that explain the lack of overlap in genes required for H2O2 tolerance after each of the three pretreatments. Together, this work shows that acquired tolerance to the same severe stress occurs by different mechanisms depending on prior cellular experiences, underscoring the context-dependent nature of stress tolerance

Cartographie des argiles gonflantes à partir de données hyperspectrales aéroportées couplées à des mesures in situ et des essais en laboratoire.

International audienceLes cartes géologiques établies et publiées par le BRGM à l’échelle du 1/50 000 ont été utilisées comme données d’entrées pour établir la cartographie départementale de l’aléa retrait-gonflement des argiles conduit par le BRGM de 1997 à fin 2010. Leur analyse permet d’identifier les formations argileuses (au sens large), affleurantes ou sub-affleurantes, et d’en établir une cartographique numérique, homogène à l’échelle départementale. En pratique, cette échelle départementale s’avère parfois insuffisante et les données géologiques sur lesquelles la cartographie a été bâtie est par endroit peu précise spatialement. En effet, les sinistres liés au retrait-gonflement des argiles se produisent principalement sur des constructions individuelles, la résolution de la carte n’est pas adaptée à l’utilisation à une échelle communale, par exemple pour la réalisation de zonages réglementaires. Il existe donc une forte demande pour une cartographie plus fine de ce phénomène. Le BRGM, à travers différents projets de recherche, travaille actuellement sur la mise en place d’une méthodologie d’exploitation des images hyperspectrales couplées à des connaissances locales en vue d’affiner la cartographie de l’aléa retrait-gonflement des argiles. Pour cela, l’approche proposée demande l’exploitation d’ensembles de données de différentes natures (bases de données géotechniques, mesures de spectroscopie infrarouge terrain et imagerie hyperspectrale) pour les intégrer dans une méthode opérationnelle de localisation et de quantification des zones riches en argiles de type gonflant en apportant une information homogène et continue aux différentes échelles pouvant intéresser les décideurs locaux. L'analyse spectrale de la lumière solaire réfléchie par la surface terrestre, ou spectroscopie de réflectance, constitue l'une des plus importantes sources d'information en ce qui concerne les caractéristiques chimiques et minéralogiques des matériaux constitutifs de la surface terrestre. Les spectres de réflectance dans l’infrarouge proche et moyen (de 1100 à 2500 nm) des roches présentent des bandes d’absorption caractéristiques qui permettent l’identification des minéraux constitutifs, par l’analyse de leur position en longueur d’onde, leur forme et leur intensité. Cette technique d’analyse spectrale à deux niveaux – proximal (laboratoire, in situ) et distal (télédétection) – est un outil de caractérisation des minéraux encore largement inexploité pour l’étude des sols gonflants.L’objectif des différents projets menés par le BRGM dans ce domaine est d’apporter à moyen terme aux différentes parties prenantes une cartographie fine permettant une meilleure connaissance du sujet mais également de nouvelles méthodes d’analyse des argiles, plus rapides et moins onéreuses que les techniques actuelles utilisées telles que la DRX ou les sondages géotechniques

Targeting and mapping expansive soils (Loiret, France): geometrical analysis of laboratory soil spectra in the short-wave infrared domain (1100-2500 nm)

Short-wave infrared (SWIR: 1100-2500 nm) reflectance spectra of soil samples, acquired under laboratory-controlled conditions, were used to estimate the swelling potentials of the soils and to use SWIR spectroscopy to improve a part of the swelling-risk map of France. A total of 332 samples were collected to the west of Orléans (France) in various geological formations and swelling-risk areas and along two (eastern and western) transects with different samples spacings. Comparisons between the swelling potentials of the soils and the swelling-risk areas of the map exhibit good correlation in the south of the sampling area; however, there are several inconsistencies in the north of the study area that highlight the necessity of locally redrawing the accepted swelling-risk map of France. The sampling interval (approximately 260 m) along the eastern transect was too sparse and does not appear to have effectively captured the smallest and/or isolated lithologies. The sampling interval along the western transect (approximately 50 m) revealed the presence of an unmapped swelling-potential zone, which was confirmed by several soil samples. The sample interval along the western transect appears to be more suitable for mapping the smallest lithologies. The presence of several samples in close proximity that exhibit the same swelling potential is a robust indication of the presence of a zone with constant swelling potential. A new swelling-risk map of the sampling area was produced based on the soil samples. The map produced by interpolation did not permit the representation of discrete lithological units, introduced spurious swelling-risk zones that however could be representative of tillage in agricultural zones. More samples are therefore needed to produce a reliable map on the scale of the sampling area. According to swelling potential uncertainty related to soil sampling and soil treatment, spectroscopy-based approach proposed here cannot be used to replace the existing swelling-risk map of France. This method permits however the rapid and low-cost estimation of the swell potentials of a large number of samples, which could be used at regional-scale to target areas where doubt remains or where infrastructure damages attributed to swelling behavior are known. At local scale, soil samples need to be properly and laboratory treated to accurately produce local revised and detailed swelling-risk maps

A web platform for storing, sharing and executing scientific workflows for Natural Risk Assessment: part 1 – data, approaches and case studies

International audienc

Contribution of physical modelling to climate-driven landslide hazard mapping: an alpine test site

EGU2012-2445The aim of this work is to develop a methodology for integrating climate change scenarios into quantitative hazard assessment and especially their precipitation component. The effects of climate change will be different depending on both the location of the site and the type of landslide considered. Indeed, mass movements can be triggered by different factors. This paper describes a methodology to address this issue and shows an application on an alpine test site. Mechanical approaches represent a solution for quantitative landslide susceptibility and hazard modeling. However, as the quantity and the quality of data are generally very heterogeneous at a regional scale, it is necessary to take into account the uncertainty in the analysis. In this perspective, a new hazard modeling method is developed and integrated in a program named ALICE. This program integrates mechanical stability analysis through a GIS software taking into account data uncertainty. This method proposes a quantitative classification of landslide hazard and offers a useful tool to gain time and efficiency in hazard mapping. However, an expertise approach is still necessary to finalize the maps. Indeed it is the only way to take into account some influent factors in slope stability such as heterogeneity of the geological formations or effects of anthropic interventions. To go further, the alpine test site (Barcelonnette area, France) is being used to integrate climate change scenarios into ALICE program, and especially their precipitation component with the help of a hydrological model (GARDENIA) and the regional climate model REMO (Jacob, 2001). From a DEM, land-cover map, geology, geotechnical data and so forth the program classifies hazard zones depending on geotechnics and different hydrological contexts varying in time

Serious games as a social learning tool in formalizing the artisanal and small-scale mining sector in African territories

International audienceThe literature states that the predominantly “top-down only” approach classically taken to formalise the complex sector of artisanal and small-scale mining (ASM) in Africa has resulted in the design of ineffective and/or incompatible regulations. This paper discusses a complementary “bottom-up as well” approach, based on the joint design, with local stakeholders—some of whom have very low literacy and education—of serious games as an educational tool combined with new management of resources and territories. These games would serve as a social learning laboratory that would (a) provide a secure framework for testing new decisions and (b) help change opinions through deliberations. This paper is theoretical and should be regarded as presenting the design and implementation of active research regarding ASM formalisation in African territories. We argue our proposal by reviewing the literature and field debates and also by applying a solid scientific foundation

A web platform for storing, sharing and executing scientific workflows for Natural Risk Assessment: part 2 -description of an interoperable architecture based on open-source components

International audienceEnabling storing, documentation, access and execution of scientific workflows is the aim of the web platform currently designed and developed by the BRGM (French Geological Survey) for the department of Natural Risk assessment. Such a platform shall insure reproducibility, allowing transparency but also improving efficiency by easing collaborative work and sharing results and practices. The scientific scope is risk assessment in the domain of natural hazard (earthquake, landslide and submersion) from the phenomenon modelling to the impact evaluation on exposed elements such as buildings. This web platform initially designed for BRGM experts aims to be in a long-term ambition an open repository for national and international experts of natural hazards. Integration and deployment of new data sets and processes will be as automatic as possible. The architecture includes a repository of data sets, documents, links and reproducible versioned workflows. It is open and discoverable through interoperable web services, each record described by metadata allowing discovery, evaluation and use. The heart of the architecture is the workflows description and execution mechanism, based on JSON and python descriptions defining acyclic graphs of processes, executed through interoperable web services (OGC WPS). They are executable as a whole or step-by-step, with detailed logs. The execution engine must ensure security, robustness, flexibility and scalability. Used in a multi-users context, it requires asynchronous mechanisms and scheduling of computations. It will be possible for a particular execution of any workflow, to register inputs, parameters and resulting computed data sets, which become new records in the repository. Data sets and workflows will be shareable between groups of users or even publishable as web services when relevant. Connecting heterogeneous scientific codes and input data sources is another challenge. While scientific codes are implemented in various technologies, data to process can be for instance relational georeferenced databases, grids and vectors data provided in various file formats, web services, internal or external data sources, already referenced in the repository or uploaded by a user. In order to enable such an integration, we define normalized code entry points and data connectors. Finally, a web interface offers access to all the functionalities, but main components are also usable through web services or even directly when relevant

Landslides risk mapping using the Vigirisks web-tool: application in Normandie (France)

International audienceLandslides threaten many parts of the world and cause many deaths and significant damage every year, and this should increase in the future due to climate change. To cope with this situation and prevent landslides impacts, a large variety of susceptibility and hazard mapping tools have been developed, either to assess current potential failure zones or to predict those that will appear in the near future. In the following, we present an application of the Vigirisks multirisks web-platform. This web-tools, developed by BRGM, propose computations allowing multi-risks mapping in a realistic manner, e.g., including cascading effects, vulnerability assessment and damages evaluation. The study site selected here is located in Diepe (Normandie, France); this is a typical case of complex flooding/landsliding processes. The Vigirisk web-tool was tested to evaluate risks when these two processes occur in the same time. We present here a simple "concomitant risks" workflow, implemented by using a weithing method