RETRACTED ARTICLE: Numerical analysis of multiphase flow in porous material     

Nadia Laredj  Karim Bendani  Hanifi Missoum  Mustapha Maliki 《Acta Geotechnica》2014,9(1):1-5

Greenhouse gas emissions, energy security and sustainability are three of the greatest contemporary global challenges to mankind today. The Sino-German Group of scientists have composed a special issue, which is a collection of diverse quality scientific works, that will try to elucidate the current developments in CO₂ geologic sequestration research to reduce greenhouse emission including measures to monitor surface leakage, groundwater quality and the integrity of caprock, while ensuring a sufficient supply of clean energy.  相似文献   

Finite Element Analyses and Experimental Investigation of Helical Micropiles     

Konstantina Papadopoulou  Harris Saroglou  Vasileios Papadopoulos 《Geotechnical and Geological Engineering》2014,32(4):949-963

Within the framework of a research program on the behaviour of a specific type of screw micropile with helical plates of 220 mm diameter, the response in axial and horizontal loadings by the finite element method and full scale in situ tests were investigated. For the axial compressive or tensile loads, the simulation of the helical plates was carried out under axisymmetric conditions as shell foundations. The cases of purely cohesive or cohesionless soils with linear elastic–perfectly plastic behaviour were studied. The influence of shear strength parameters and the number of helical plates on the characteristic-ultimate resistance were also analyzed. For the horizontal loads 3D F.E. programs were applied for the analyses of the micropiles either as short or long ones. The in situ tests, which are presented in this article, were performed in two areas with representative subsoil conditions. The respective predictions from the F.E. method were based on results of geotechnical investigations and compared with the results of the in situ tests. A good approximation was ascertained, especially for uplift and horizontal loads and the differences were commented.  相似文献   

Using detrital garnets to determine provenance: a case study from the Vertiskos Unit (Serbomacedonian Massif,N. Greece)     

Ioannis K. Georgiadis  Antonios Koroneos  Lamprini Papadopoulou  Nikolaos Kantiranis  Alexios E. Tamparopoulos  Ananias Tsirambides 《Mineralogy and Petrology》2014,108(2):187-206

Garnet single crystals of several millimeters in diameter were collected from the uppermost horizon of a soil profile developing immediately on the gneissic rocks of the Vertiskos Unit of the Serbomacedonian Massif in northern Greece. The garnets were analyzed for major elements by EDS analyzer mounted on a scanning electron microscope, and the obtained data were utilized to determine their source rocks. Bivariate diagrams, spider diagrams as well as statistical analysis were used in order to correlate and compare the garnet composition of the basement rocks of the Vertiskos Unit with the existing reference data. This case study demonstrates the difficulty in assigning a source rock to sediment, using only the chemical compositional of detrital garnet. Direct linking of the detrital garnets and the outcropping rocks is not always possible despite well documented outcrop lithologies. This is largely due to a complex metamorphic evolution that leads to overlapping compositions between garnets originating from different lithologies that have undergone similar metamorphic processes and alteration effects.  相似文献   

Towards Better WMS Maps Through the Use of the Styled Layer Descriptor and Cartographic Conflict Resolution for Linear Features     

Ionuţ Iosifescu Enescu  Nadia H. Panchaud  Magnus Heitzler  Cristina M. Iosifescu Enescu  Lorenz Hurni 《The Cartographic journal》2013,50(2):125-136

Abstract

Mercator depicted Croatia on several general maps. In accordance with the level of geographical knowledge, map scales and technical possibilities of the time, Mercator provided a relatively detailed depiction of basic geographical features on these maps. His interest in mapping Croatia was probably motivated by the fact that the Venetian Republic, the Habsburg Monarchy and the Ottoman Empire had fought over this area in the sixteenth century, contributing to the fragmentation of the medieval Croatian State, while at the same time facilitating economic, religious, linguistic, artistic and scientific communication between Central, South East and Mediterranean Europe. Mercator paid special attention to toponyms that enabled geographical objects to be identified and the decoding of cartographic contents. Research into Mercator’s maps has shown that geographical names, among other things, clearly indicate the sources of spatial data that he used. Additionally, geographical names on Mercator’s maps are significant indicators of the linguistic and cultural contacts that were particularly prominent in border areas, for example, along the eastern Adriatic coast, or the courses of the Danube, Sava and Drava.  相似文献   

Physical chemical analysis of marine sediment cementation from the Gulf of Guinea     

Xianfeng Liu  Tammam Hammad  Nadia Saiyouri  Mahdia Hattab 《Comptes Rendus Geoscience》2012,344(9):461-470

This study aims at investigating the cementation of marine sediments from the Gulf of Guinea by using physicochemical analysis. In order to highlight the presence of cementation in the sediments, three conventional consolidation tests were conducted on intact and remoulded samples. Mercury intrusion porosimetry analyses were then carried out on the specimens taken from samples after consolidation tests. Several physicochemical experimental techniques were used to analyze these cementations, such as cation exchange capacity analysis, batch test, scanning electron microscope imaging coupled with EDS chemical analysis, and thermal analysis. The results seem to indicate that the cementation of these sediments is predominated by the presence of smectite gel between clay aggregates (clusters). Finally, a conceptual sediment microstructural model is proposed to describe the cementation.  相似文献   

IT-OSRA: applying ensemble simulations to estimate the oil spill risk associated to operational and accidental oil spills     

Antonio Augusto Sepp Neves  Nadia Pinardi  Flavio Martins 《Ocean Dynamics》2016,66(8):939-954

Oil Spill Risk Assessments (OSRAs) are widely employed to support decision making regarding oil spill risks. This article adapts the ISO-compliant OSRA framework developed by Sepp Neves et al. (J Environ Manag 159:158–168, 2015) to estimate risks in a complex scenario where uncertainties related to the meteo-oceanographic conditions, where and how a spill could happen exist and the risk computation methodology is not yet well established (ensemble oil spill modeling). The improved method was applied to the Algarve coast, Portugal. Over 50,000 simulations were performed in 2 ensemble experiments to estimate the risks due to operational and accidental spill scenarios associated with maritime traffic. The level of risk was found to be important for both types of scenarios, with significant seasonal variations due to the the currents and waves variability. Higher frequency variability in the meteo-oceanographic variables were also found to contribute to the level of risk. The ensemble results show that the distribution of oil concentrations found on the coast is not Gaussian, opening up new fields of research on how to deal with oil spill risks and related uncertainties.  相似文献   

A relocatable ocean model in support of environmental emergencies     

Michela De Dominicis  Silvia Falchetti  Francesco Trotta  Nadia Pinardi  Luca Giacomelli  Ernesto Napolitano  Leopoldo Fazioli  Roberto Sorgente  Patrick J. Haley Jr.  Pierre F. J. Lermusiaux  Flavio Martins  Michele Cocco 《Ocean Dynamics》2014,64(5):667-688

During the Costa Concordia emergency case, regional, subregional, and relocatable ocean models have been used together with the oil spill model, MEDSLIK-II, to provide ocean currents forecasts, possible oil spill scenarios, and drifters trajectories simulations. The models results together with the evaluation of their performances are presented in this paper. In particular, we focused this work on the implementation of the Interactive Relocatable Nested Ocean Model (IRENOM), based on the Harvard Ocean Prediction System (HOPS), for the Costa Concordia emergency and on its validation using drifters released in the area of the accident. It is shown that thanks to the capability of improving easily and quickly its configuration, the IRENOM results are of greater accuracy than the results achieved using regional or subregional model products. The model topography, and to the initialization procedures, and the horizontal resolution are the key model settings to be configured. Furthermore, the IRENOM currents and the MEDSLIK-II simulated trajectories showed to be sensitive to the spatial resolution of the meteorological fields used, providing higher prediction skills with higher resolution wind forcing.  相似文献   

Experimental investigation of microstructural changes in soils eroded by suffusion using X-ray tomography   总被引：1，自引：0，他引：1  

Nguyen  Cong Doan  Benahmed  Nadia  Andò  Edward  Sibille  Luc  Philippe  Pierre 《Acta Geotechnica》2019,14(3):749-765

Internal erosion is a complex phenomenon which represents one of the main risks to the safety of earthen hydraulic structures such as embankment dams, dikes or levees. Its occurrence may cause instability and failure of these structures with consequences that can be dramatic. The specific mode of erosion by suffusion is the one characterized by seepage flow-induced erosion, and the subsequent migration of the finest soil particles through the surrounding soil matrix mostly constituted of large grains. Such a phenomenon can lead to a modification of the initial microstructure and, hence, to a change in the physical, hydraulic and mechanical properties of the soil. A direct comparison of the mechanical behaviour of soil before and after erosion is often used to investigate the impact of internal erosion on soil strength (shear strength at peak and critical state) using triaxial tests. However, the obtained results are somehow contradictory, as for instance in Chang’s study (Chang and Zhang in Geotech Test J 34(6):579–589, 2011), where it is concluded that the drained strength of eroded soil decreases compared to non-eroded soil, while both Xiao and Shwiyhat (Geotech Test J 35(6):890–900, 2012) and Ke and Takahashi (Geotech Test J 37(2):347–364, 2014) have come to the opposite conclusion. A plausible explanation of these contradictions might be attributed to the rather heterogeneous nature of the suffusion process and to the way the coarse and fine grains are rearranged afterwards leading to a heterogeneous soil structure, a point that, for now, is not taken into account, nor even mentioned, in the existing analyses. In the present study, X-ray computed tomography (X-ray CT) is used to follow the microstructure evolution of a granular soil during a suffusion test, and, therefore, to capture the induced microstructural changes. The images obtained from X-ray CT reveal indeed that fine particles erosion is obviously not homogeneous, highlighting the existence of preferential flow paths that lead to a heterogeneous sample in terms of fine particles, void ratio and inter-granular void ratio distribution.

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Surface-wave analysis for static corrections in mineral exploration: A case study from central Sweden     

Myrto Papadopoulou  Federico Da Col  Binbin Mi  Emma Bäckström  Paul Marsden  Bojan Brodic  Alireza Malehmir  Laura Valentina Socco 《Geophysical Prospecting》2020,68(1):214-231

In mineral exploration, increased interest towards deeper mineralizations makes seismic methods attractive. One of the critical steps in seismic processing workflows is the static correction, which is applied to correct the effect of the shallow, highly heterogeneous subsurface layers, and improve the imaging of deeper targets. We showed an effective approach to estimate the statics, based on the analysis of surface waves (groundroll) contained in the seismic reflection data, and we applied it to a legacy seismic line acquired at the iron-oxide mining site of Ludvika in Sweden. We applied surface-wave methods that were originally developed for hydrocarbon exploration, modified as a step-by-step workflow to suit the different geologic context of hard-rock sites. The workflow starts with the detection of sharp lateral variations in the subsurface, the existence of which is common at hard-rock sites. Their location is subsequently used, to ensure that the dispersion curves extracted from the data are not affected by strong lateral variations of the subsurface properties. The dispersion curves are picked automatically, windowing the data and applying a wavefield transform. A pseudo-2D time-average S-wave velocity and time-average P-wave velocity profile are obtained directly from the dispersion curves, after inverting only a reference curve. The time-average P-wave velocity profile is then used for the direct estimation of the one-way traveltime, which provides the static corrections. The resulting P-wave statics from the field data were compared with statics computed through conventional P-wave tomography. Their difference was mostly negligible with more than 91% of the estimations being in agreement with the conventional statics, proving the effectiveness of the proposed workflow. The application of the statics obtained from surface waves provided a stacked section comparable with that obtained by applying tomostatics.  相似文献   

Linking 1D coastal ocean modelling to environmental management: an ensemble approach   总被引：1，自引：1，他引：0  

Giulia Mussap  Marco Zavatarelli  Nadia Pinardi 《Ocean Dynamics》2017,67(12):1627-1644

The use of a one-dimensional interdisciplinary numerical model of the coastal ocean as a tool contributing to the formulation of ecosystem-based management (EBM) is explored. The focus is on the definition of an experimental design based on ensemble simulations, integrating variability linked to scenarios (characterised by changes in the system forcing) and to the concurrent variation of selected, and poorly constrained, model parameters. The modelling system used was previously specifically designed for the use in “data-rich” areas, so that horizontal dynamics can be resolved by a diagnostic approach and external inputs can be parameterised by nudging schemes properly calibrated. Ensembles determined by changes in the simulated environmental (physical and biogeochemical) dynamics, under joint forcing and parameterisation variations, highlight the uncertainties associated to the application of specific scenarios that are relevant to EBM, providing an assessment of the reliability of the predicted changes. The work has been carried out by implementing the coupled modelling system BFM-POM1D in an area of Gulf of Trieste (northern Adriatic Sea), considered homogeneous from the point of view of hydrological properties, and forcing it by changing climatic (warming) and anthropogenic (reduction of the land-based nutrient input) pressure. Model parameters affected by considerable uncertainties (due to the lack of relevant observations) were varied jointly with the scenarios of change. The resulting large set of ensemble simulations provided a general estimation of the model uncertainties related to the joint variation of pressures and model parameters. The information of the model result variability aimed at conveying efficiently and comprehensibly the information on the uncertainties/reliability of the model results to non-technical EBM planners and stakeholders, in order to have the model-based information effectively contributing to EBM.  相似文献