CNRS School and Observatory of Earth Sciences

Strasbourg, France

CNRS School and Observatory of Earth Sciences

Strasbourg, France
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Jeong S.W.,Korea Institute of Geoscience and Mineral Resources | Locat J.,Laval University | Leroueil S.,Laval University | Malet J.-P.,CNRS School and Observatory of Earth Sciences
Canadian Geotechnical Journal | Year: 2010

Rheological properties of fine-grained sediments depending on index properties and salinity were examined. To characterize flow behaviors as a function of soil type, groups were made for convenience: (i) low-activity clays (group 1), (ii) high-activity clays (group 2), and (iii) silt-rich soils (especially for iron tailings; group 3). Low-activity and high-activity clays have characteristics of pseudoplastic (shear thinning) fluids, and exhibit a decrease in viscosity with increasing shear rate. However, in terms of the change in soil structure due to particle-particle interactions, illitic and montmorillonitic clays have opposite responses to salinity. As most of our data were obtained on low-activity clays - mostly illitic mixtures - we implemented a test program to ascertain the influence of montmorillonite on flow behavior. Using the Bingham model, a simple relationship is presented in terms of the possible critical limits of rheological transitions from clay- to silt- to sand-rich soils.

Riehl A.,CNRS Hydrology and Geochemistry Laboratory of Strasbourg | Elsass F.,French National Institute for Agricultural Research | Duplay J.,CNRS Hydrology and Geochemistry Laboratory of Strasbourg | Huber F.,CNRS Hydrology and Geochemistry Laboratory of Strasbourg | Trautmann M.,CNRS School and Observatory of Earth Sciences
Geoderma | Year: 2010

Fluidized bed combustion ash (FBC) is a by-product from coal-fired power stations used for many decades in concrete, cement and brick manufacturing and more recently for trace metal immobilization and pesticide retention in soils. Moreover FBC ash has been recommended by some authors as a soil amendment in agriculture for its nutrient supply. In this study silico-aluminous (SiAl) and sulfo-calcic (SCa) fly ashes have been added to a fluvisol (calcaric) sampled in the Rhine River plain (Germany) in order to investigate the physical, chemical and physico-chemical possible modifications of the amended soil. Earthworms were introduced into microcosms hydrated with a solution of water and CaCl2 (3.7 10- 4 mg/L; pH = 6.2) and stabilized during 7 and 14 weeks. Batch leaching tests were performed during 6 weeks on the amended soil in order to obtain data on the mobilization potential of major elements (NH4+, Na+, K+, Mg2+, Cl-, Ca2+, NO3-, SO42-, PO43-, H4SiO4) and trace elements (Sr, Ba, V, Zn, Cu, Co, As, Ni, Mo, Cr, Cd, Pb) during ash-soil-water interactions. The main modification is an increase in pH (≈ 12) of soil water in soil amended with sulfo-calcic ash, whereas soil pH only slightly changes in the other soil as compared to control soil. This alkaline pH causes a strong mortality of the macrofauna and a higher mobility of Co, Ni and V on the contrary to Cr, Cu, Pb and Zn which are less mobile and more strongly retained by soil. Soil physico-chemical properties remain generally similar to control soil in soil amended with silico-aluminous ash (SiAl) but show major differences in the case of soil amended with sulfo-calcic ash (SCa). The sulfo-calcic ash therefore seems less adapted to integration in soils from an agricultural and farming point of view, contrary to the silico-aluminous ash which increases the cation exchange capacity, thus improving the nutrient and water reserve for plants. © 2009 Elsevier B.V. All rights reserved.

Ertlen D.,French National Center for Scientific Research | Schwartz D.,French National Center for Scientific Research | Trautmann M.,CNRS School and Observatory of Earth Sciences | Webster R.,Rothamsted Research | Brunet D.,Montpellier SupAgro
European Journal of Soil Science | Year: 2010

The absorbance of near-infrared (NIR) radiation by plants depends on the overtones of vibration, bending and stretching of the chemical bonds within their organic components. The wide variety of these bonds gives rise to characteristic NIR spectra, or 'fingerprints', of plant materials. Do these fingerprints remain in the soil when the plants decompose and allow discrimination between soils that have supported different types of vegetation? We have compared the NIR spectra of grassland soil with those of soil under forest in the Vosges mountains in France. Near-infrared reflectances, R, from 370 samples of soil were recorded as A = log10(1/R) at wavelengths between 1100 and 2500 nm and averaged over 10-nm intervals to give spectra each with 140 values. A canonical variate analysis (CVA) of the raw spectra discriminated well, but not perfectly, between grassland and forest soil, with Mahalanobis distance, D, of 4.87. Standardization along the spectra to remove effects of varied mineral composition achieved complete separation between the two sources with D = 9.81. Canonical variate analysis of first and second derivatives of the spectra distinguished the two groups even better, with D = 12.27 and D = 16.65, respectively.The results show much promise for inferring past vegetative cover from NIR spectra deriving from the organic matter in the soil. The next step will be to extend these studies to see how well we can distinguish other types of vegetation from such spectra. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science.

Razak K.A.,University of Twente | Razak K.A.,University of Technology Malaysia | Straatsma M.W.,University of Twente | van Westen C.J.,University of Twente | And 2 more authors.
Geomorphology | Year: 2011

Mapping complex landslides under forested terrain requires an appropriate quality of digital terrain models (DTMs), which preserve small diagnostic features for landslide classification such as primary and secondary scarps, cracks, and displacement structures (flow-type and rigid-type). Optical satellite imagery, aerial photographs and synthetic aperture radar images are less effective to create reliable DTMs under tree coverage. Here, we utilized a very high density airborne laser scanning (ALS) data, with a point density of 140 points m-2 for generating a high quality DTM for mapping landslides in forested terrain in the Barcelonnette region, the Southern French Alps. We quantitatively evaluated the preservation of morphological features and qualitatively assessed the visualization of ALS-derived DTMs. We presented a filter parameterization method suitable for landslide mapping and compared it with two default filters from the hierarchical robust interpolation (HRI) and one default filter from the progressive TIN densification (PTD) method. The results indicate that the vertical accuracy of the DTM derived from the landslide filter is about 0.04m less accurate than that from the PTD filter. However, the landslide filter yields a better quality of the image for the recognition of small diagnostic features as depicted by expert image interpreters. Several DTM visualization techniques were compared for visual interpretation. The openness map visualized in a stereoscopic model reveals more morphologically relevant features for landslide mapping than the other filter products. We also analyzed the minimal point density in ALS data for landslide mapping and found that a point density of more than 6 points m-2 is considered suitable for a detailed analysis of morphological features. This study illustrates the suitability of high density ALS data with an appropriate parameterization for the bare-earth extraction used for landslide identification and characterization in forested terrain. © 2010 Elsevier B.V.

Luna B.Q.,University of Twente | Cepeda J.,Norwegian Geotechnical Institute | Stumpf A.,CNRS School and Observatory of Earth Sciences | Van Westen C.J.,University of Twente | And 3 more authors.
Landslide Science and Practice: Spatial Analysis and Modelling | Year: 2013

The main goals of landslide run-out modeling should be the assessment of future landslide activity with a range of potential scenarios, and the information of the local populations about the hazards in order to enable informed response measures. In recent times, numerical dynamic run-out models have been developed which can assess the velocity and extent of motion of rapid landslides such as debris flows and avalanches, flow slides and rock avalanches. These models are physically-based and solved numerically, simulating the movement of the flow using constitutive laws of fluid mechanics in one or two dimensions. Resistance parameters and release volumes are crucial for a realistic simulation of the landslide behavior, whereas it is generally difficult to measure them directly in the field. Uncertainties in the parameterization of these models yield many uncertainties concerning their frequency values, which must be addressed in a proper risk assessment. Based on the probability density functions of release volumes and friction coefficients of a given landslide model, this work aims to systematically quantify the uncertainties in the runout modeling. The obtained distributions can be used as an input for a probabilistic methodology where the uncertainties in the release volume and friction coefficients (rheological parameters) inside the dynamic models can be addressed. This will improve the confidence of the dynamic run-out model outputs such as the distribution of deposits in the run-out area, velocities and impact pressures, important components for a risk analysis and regulatory zoning. © Springer-Verlag Berlin Heidelberg 2013.

Niethammer U.,University of Stuttgart | James M.R.,Lancaster University | Rothmund S.,University of Stuttgart | Travelletti J.,CNRS School and Observatory of Earth Sciences | Joswig M.,University of Stuttgart
Engineering Geology | Year: 2012

Unmanned aerial vehicles (UAVs) equipped with digital compact cameras can be used to map landslides quickly and at a high ground resolution. Images taken by a radio-controlled mini quad-rotor UAV of the Super-Sauze, France landslide have been used to produce a high-resolution ortho-mosaic of the entire landslide and digital terrain models (DTMs) of several regions. The UAV capability for imaging fissures and displacements on the landslide surface has been evaluated, and the subsequent image processing approaches for suitably georectifying the data have been assessed. For Super-Sauze, horizontal displacements of 7 to 55. m between a high-resolution airborne ortho-photo of May 2007 and a UAV-based ortho-mosaic of October 2008 have been measured. Fixed areas of persistent deformation have been identified, producing fissures of different distributions and orientations comparable to glacial crevasses, and relating directly to the bedrock topography. The UAV has demonstrated its capability for producing valuable landslide data but improvements are required to reduce data processing time for the efficient generation of ortho-mosaics based on photogrammetric DTMs, in order to minimise georeferencing errors. © 2011 Elsevier B.V.

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