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1.
Détection des cavités à l'aide de mesures électriques et du géoradar dans une galerie d'amenée d'eau
Old water-delivery tunnels can become leaky and produce water losses of some economic importance. The detection of solution cavities behind the concrete lining was the purpose of an investigation in a 2 km long part of a water-delivery tunnel in Switzerland. A gypsum zone of about 700 m length was considered to be especially critical. Two geophysical methods were used at the same time: resistivity profiling with three different array lengths, and ground-penetrating radar. The cavities were characterized by higher electrical resistivity, principally for the short array (AB = 3 m). Detailed measurements with a pole-dipole array were made for a better depth interpretation of anomalies in some critical zones. The GPR investigations were made with an antenna of 500 MHz. Some transverse profiles were carried out with GPR in order to better delineate the discovered cavernous or weathered zones. GPR located cavities up to a few meters in length, at depths between 0 and 4 m behind the lining. Anomalies found by one investigation method were often confirmed by the other one. Their complementarity thus allowed a more reliable interpretation of the gathered data. Verifying drillholes have mostly confirmed the good correlation between geophysical interpretation and drilling results. Endoscopic investigations in the drillholes enabled us to have a real vision of discovered cavities.Although GPR-profiling has the advantage of a continuous underground imaging and of greater efficiency during data acquisition (investigation speed) we consider the combination of both methods in the present study as a good example of an integrated geophysical survey, which enables a more reliable interpretation of the gathered data.
Résumé
Les galeries d'amenée d'eau d'un certain âge peuvent poser des problèmes à cause de pertes d'eau parfois importantes. L'objectif de cette étude a été la mise en évidence et le positionnement de cavités derrière le revêtement d'une galerie en Suisse, sur une longueur de 2 km. Une zone de gypse longue de 700 m était considérée comme particulièrement critique. Deux méthodes géophysiques ont été conjointement utilisées: le traîné électrique multiple avec trois longueurs de ligne d'envoi de courant et le géoradar. Les cavités, caractérisées par des résistivités élevées, ont surtout été mises en évidence par le dispositif le plus court (AB = 3 m). Des mesures de détail ont été réalisées dans les zones critiques avec un dispositif pôle-dipôle en vue d'une meilleure interprétation des anomalies en profondeur. Les mesures de géoradar ont été exécutées avec une antenne de 500 MHz. Quelques profils transversaux ont été effectués pour vérifier l'extension des zones d'altérations ou des cavités. Le géoradar a pu localiser des cavités mesurant jusqu'à plusieurs mètres en longueur à des profondeurs variant entre 0 et 4 m derrière le revêtement de la galerie. Les anomalies décelées par une méthode ont souvent pu être confirmées par l'autre et leur complémentarité a permis une interprétation plus sûre. Des forages carottés ont montré une bonne corrélation entre les anomalies géophysiques et la réalité. Des mesures de fibroscopie dans les forages nous ont permis de déterminer la géométrie des cavités.Le géoradar possède des avantages certains: imagerie continue du massif rocheux et grande rapidité dans l'acquisition des données. Néanmoins, nous considérons la combinaison des deux méthodes utilisées dans cette étude comme le bon exemple d'une investigation géophysique combinée permettant une interprétation optimale de tous les résultats. 相似文献2.
Questionnaires were completed by 2306 beach users at 19 Welsh beaches with respect to beach selection parameters. The modal group of respondents was female aged 30–39. Beach choice was primarily determined by clean litter-free sand and seawater, followed by safety. Refreshment facilities and beach awards were deemed minor considerations by the public when choosing a beach to visit. Approximately 58 per cent of respondents were aware of beach award and rating schemes. Of coastal visitors interviewed for this paper, 67 per cent rated a beach as 'important' or 'very important' to their holiday, with just 2 per cent replying that they were unimportant. 相似文献
3.
L. Vandenbulcke J.-M. Beckers A. Barth M. Aidonidis F. Ardhuin C. Fratianni D. Pallela M. Tudor P. Martin M. Rixen 《Progress in Oceanography》2009,82(3):149-167
The prediction of surface drift of floating objects is an important task, with applications such as marine transport, pollutant dispersion, and search-and-rescue activities. But forecasting even the drift of surface waters is very challenging, because it depends on complex interactions of currents driven by the wind, the wave field and the general prevailing circulation. Furthermore, although each of those can be forecasted by deterministic models, the latter all suffer from limitations, resulting in imperfect predictions. In the present study, we try and predict the drift of two buoys launched during the DART06 (Dynamics of the Adriatic sea in Real-Time 2006) and MREA07 (Maritime Rapid Environmental Assessment 2007) sea trials, using the so-called hyper-ensemble technique: different models are combined in order to minimize departure from independent observations during a training period; the obtained combination is then used in forecasting mode. We review and try out different hyper-ensemble techniques, such as the simple ensemble mean, least-squares weighted linear combinations, and techniques based on data assimilation, which dynamically update the model’s weights in the combination when new observations become available. We show that the latter methods alleviate the need of fixing the training length a priori, as older information is automatically discarded.When the forecast period is relatively short (12 h), the discussed methods lead to much smaller forecasting errors compared with individual models (at least three times smaller), with the dynamic methods leading to the best results. When many models are available, errors can be further reduced by removing colinearities between them by performing a principal component analysis. At the same time, this reduces the amount of weights to be determined.In complex environments when meso- and smaller scale eddy activity is strong, such as the Ligurian Sea, the skill of individual models may vary over time periods smaller than the forecasting period (e.g. when the latter is 36 h). In these cases, a simpler method such as a fixed linear combination or a simple ensemble mean may lead to the smallest forecast errors. In environments where surface currents have strong mean-kinetic energies (e.g. the Western Adriatic Current), dynamic methods can be particularly successful in predicting the drift of surface waters. In any case, the dynamic hyper-ensemble methods allow to estimate a characteristic time during which the model weights are more or less stable, which allows predicting how long the obtained combination will be valid in forecasting mode, and hence to choose which hyper-ensemble method one should use. 相似文献
4.
A cobble beach (-6 diameter to -8 diameter) located on the South Wales coastline, UK, was studied over a three-month winter period to assess litter input levels. After total beach litter clearance, six surveys were conducted at consecutive spring tides which involved marking of previously unrecorded litter. The beach was soon inundated with debris, predominantly plastic beverage containers. Some marked litter was found to disappear from the beach surface, re-emerging weeks later which suggests that the potential for litter burial has been underestimated in litter research. Higher wave energies between surveys coincided with higher levels of previously unseen litter. These new inputs consisted of sea borne and exhumed litter. Items larger than the surrounding cobbles were found to work their way back to the surface of the beach after burial, smaller items remained buried. Pits dug into the cobble ridge confirmed the burial of mainly small items. 相似文献
5.
Abstract: The Alpine Orogen contains in South East Europe, from the Carpathians to the Balkans–Srednogorie, an Upper Cretaceous, ore bearing igneous belt: a narrow elongated body which runs discontinously from the Apuseni Mountains in the North, to the western part of the South Carpathians (Banat) in Romania, and further South to the Carpathians of East Serbia and still further East to Srednogorie (Bulgaria). This results in a belt of 750 km/30–70 km, bending from N-S in Romania and Serbia, to E-W in Bulgaria. Using the well established century-old terminology of this region, we describe it in this paper as the Banatitic Magmatic and Metallogenetic Belt (BMMB). Plate tectonics models of the Alpine evolution of South East Europe involve Mesozoic rifting, spreading and thinning of the continental crust or formation of oceanic crust in the Tethian trench system, followed by Cretaceous-Tertiary convergence of Africa with Europe and opening of Eastern Mediterranean and Black Sea troughs. The result of successive stages in the collision process is not only the continental growth of Europe from N to S by the docking of several microplates formerly separated from it by Mesozoic palaeo–oceans, but also the rise of mountain belts by overthickening of the crust, followed by orogenic collapse, lateral extrusion, exhumation of metamorphic core complexes and post-collisional magmatism connected to strike-slip or normal faulting. The BMMB of the Carpathian-Balkan fold belt is rich in ore deposits related to plutons and/or volcano-plutonic complexes. Serbian authors have proposed an Upper Cretaceous Paleorift in Eastern Serbia for the Timok zone and some Bulgarian geologists have furnished geologic, petrological and metallogenetic support for this extensional model along the entire BMMB. The existence and importance of previous westwards directed subductions of Transilvanides (=South Apuseni = Mure? Zone) and Severin-Krajina palaeo–oceans, popular in Roman ian literature, seems to have little relevance to BMMB generation, but the well documented northwards directed subduction of the Vardar-Axios palaeo–ocean during Jurassic and Lower Cretaceous is a good pre-condition for the generation, during the Upper Cretaceous, of banatitic magmas in extensional regime, by mantle delamination due to slab break–off. Four magmatic trends are found: a tholeiitic trend, a calc-alkaline trend, a calc-alkaline high–K to shoshonitic trend and, restricted to East Srednogorie, a peralkaline trend. For acid intrusives, the typology is clearly I-type and magnetite–series, pointing to sources in the deep crust or the mantle; however, some high 87Sr/86Sr ratios recorded in banatites prove important contamination from the upper crust. The calc-alkaline hydrated magmas, most common for banatitic plutons, can be considered as recording three stages of evolution: more primitive – the monzodioritic, dioritic to granodioritic trend (S Apuseni, S Ba–nat, Timok, C and W Srednogorie); more evolved – the granodioritic-granitic trend (N Apuseni, N Banat, Ridanj–Krepoljin); the alkaline trend (E and W Srednogorie, western part of N Banat). Correlating the composition of the host plutons with the types of mineralisation, several environments can be found in the BMMB, function of timing of fluid separation (porphyry versus non-porphyry environments), depth of emplacement, size of intrusion and geology of intruded rock pile, biotite versus hornblende crystallisation, involving the evolution of K/Na ratio in fluids, i. e. development of potassic and phyllic alteration zones: a) non-porphyry environment with granodioritic to granitic magmas, plutonic level, skarn mineralisation prevails; b) porphyry environment with monzodioritic or dioritic to granodioritic magmas, subvolcanic–hypabyssal–plutonic level; porphyry Cu with skarn halo at hypabyssal-subvolcanic level; c) porphyry environment with monzodioritic or dioritic to granodioritic magmas, volcano-plutonic complexes with porphyry copper plus massive sulfide mineralisation at subvolcanic-volcanic level; d) non-porphyry environment with magmas of alkaline tendency, volcanic level, vein (“mesothermal” and “epithermal”) mineralisation. 相似文献
6.
The saturation in water or hydrocarbon is an important petrophysical parameter used for the evaluation of oil and gas reservoirs. It represents the amount of hydrocarbons in a reservoir. There are many relations to determine the water saturation from well logs by using the physical properties of rocks. The accurate determination of the hydrocarbon formation or the water saturation is given by the accuracy of the parameters used for calculating and by the relations used. 相似文献
7.
Cornel Olariu Ronald J. Steel Nataleigh K. Vann Eugen P. Tudor Moonsoo Shin René R. Winter Yuqian Gan Eunsil Jung Flavio N. De Almeida Jr. Gabriel Giacomone Daniel Minisini Walter Brinkworth Maria L. Loss Juan Iñigo Raul Gutierrez 《Basin Research》2020,32(2):279-292
Seismic-reflection data show that most deepwater (>200 m water depth) basins are filled by sand and mud dispersed across clinoformal geometries characterized by gently dipping topsets, steeper foresets and gently dipping bottomsets. However, the entire geometry of these ubiquitous clinoforms is not always recognized in outcrops. Sometimes the infill is erroneously interpreted as “layer cake” or “ramp” stratigraphy because the topset-foreset-bottomset clinoforms are not well exposed. Regional 2-D seismic lines show clinoforms in the Lower to Middle Jurassic Challaco, Lajas, and Los Molles formations in S. Neuquén Basin in Argentina. Time equivalent shelf, slope and basin-floor segments of clinoforms are exposed, and can be walked out in hundreds of metres thick and kilometres-wide outcrops. The studied margin-scale clinoforms are not representing a continental-margin but a deepwater shelf margin that built out in a back-arc basin. Lajas-Los Molles clinoforms have been outcrop-mapped by tracing mudstones interpreted as flooding surfaces on the shelf and abandonment surfaces (low sedimentation rate) in the deepwater basin. The downslope and lateral facies variability in the outcrops is also consistent with a clinoform interpretation. The Lajas topset (shelf) is dominated by fluvial and tidal deposits. The shelf-edge rollover zone is occasionally occupied by a 40–50-m-thick coarse-grained shelf-edge delta, sometimes incising into the underlying slope mudstones, producing oblique clinoforms expressing toplap erosion on seismic. A muddy transgressive phase capping the shelf-edge deltas contains tidal sandbodies. Shelf-edge deltas transition downslope into turbidite- and debris flow-filled channels that penetrate down the mud-prone Los Molles slope. At the base-of-slope, some 300m below the shelf edge, there are basin-floor fan deposits (>200 m thick) composed of sandy submarine-fan lobes separated by muddy abandonment intervals. The large-scale outcrop correlation between topset–foreset–bottomset allows facies and depositional interpretation and sets outcrop criteria recognition for each clinoform segment. 相似文献
8.
Alpine polyphase tectono-metamorphic evolution of the South Carpathians: A new overview 总被引：2，自引：0，他引：2
Viorica Iancu Tudor Berza Antoneta Seghedi Ion Gheuca Horst-Peter Hann 《Tectonophysics》2005,410(1-4):337-365
The main terrains involved in the Cretaceous–Tertiary tectonism in the South Carpathians segment of the European Alpine orogen are the Getic–Supragetic and Danubian continental crust fragments separated by the Severin oceanic crust-floored basin. During the Early–Middle Cretaceous times the Danubian microplate acted initially as a foreland unit strongly involved in the South Carpathians nappe stacking. Multistage folding/thrusting events, uplift/erosion and extensional stages and the development of associated sedimentary basins characterize the South Carpathians during Cretaceous to Tertiary convergence and collision events. The main Cretaceous tectogenetic events responsible for contraction and crustal thickening processes in the South Carpathians are Mid-Cretaceous (“Austrian phase”) and Latest Cretaceous (“Laramide” or “Getic phase”) in age. The architecture of the South Carpathians suggests polyphase tectonic evolution and mountain building and includes from top to bottom: the Getic–Supragetic basement/cover nappes, the Severin and Arjana cover nappes, and Danubian basement/cover nappes, all tectonically overriding the Moesian Platform. The Severin nappe complex (including Obarsia and Severin nappes) with Late Jurassic–Early Cretaceous ophiolites and turbidites is squeezed between the Danubian and Getic–Supragetic basement nappes as a result of successive thrusting of dismembered units during the inferred Mid- to Late Cretaceous subduction/collision followed by tectonic inversion processes.
Early Cretaceous thick-skinned tectonics was replaced by thin-skinned tectonics in Late Cretaceous. Thus, the former Middle Cretaceous “Austrian” nappe stack and its Albian–Lower Senonian cover got incorporated in the intra-Senonian “Laramide/Getic” stacking of the Getic–Supragetic/Severin/Arjana nappes onto the Danubian nappe duplex. The two contraction events are separated by an extensional tectonic phase in the upper plate recorded by the intrusion of the “Banatitic” magmas (84–73 Ma). The overthrusting of the entire South Carpathian Cretaceous nappe stack onto the fold/thrust foredeep units and to the Moesian Platform took place in the Late Miocene (intra-Sarmatian) times and was followed by extensional events and sedimentary basin formation. 相似文献
9.
Aaron Zimmerman Holly J. Stein Judith L. Hannah Dejan Koželj Kamen Bogdanov Tudor Berza 《Mineralium Deposita》2008,43(1):1-21
The Apuseni–Banat–Timok–Srednogorie magmatic–metallogenic belt (ABTS belt), forms a substantial metallogenic province in the
Balkan-South Carpathian system in southeastern Europe. The belt hosts porphyry, skarn, and epithermal deposits mined since
pre-Roman times. Generally, the deposits, prospects, and occurrences within the belt are linked to magmatic centers of calc-alkaline
affinity. Fifty-one rhenium-osmium (Re–Os) ages and Re concentration data for molybdenites define systematic geochronologic
trends and constrain the geochemical-metallogenic evolution of the belt in space and time. From these data and additional
existing geologic-geochemical data, a general tectonic history for the belt is proposed. Mineralization ages in Apuseni-Banat,
Timok, and Panagyurishte (the central district of the larger E–W Srednogorie Zone) range from 72–83, 81–88, and 87–92 Ma,
respectively, and clearly document increasing age from the northwestern districts to the southeastern districts. Further,
Re–Os ages suggest rapidly migrating pulses of Late Cretaceous magmatic–hydrothermal activity with construction of deposits
in ~1 m.y., districts in ~10 m.y., and the entire 1,500 km belt in ~20 m.y. Ages in both Timok and Panagyurishte show systematic
younging, while deposit ages in Banat and Apuseni are less systematic reflecting a restricted evolution of the tectonic system.
Systematic differences are also observed for molybdenite Re concentrations on the belt scale. Re concentrations generally
range from hundreds to thousands of parts per million, typical of subduction-related Cu–Au–Mo–(PGE) porphyry systems associated
with the generation of juvenile crust. The geochronologic and geochemical trends are compatible with proposed steepening of
subducting oceanic slab and relaxation of upper continental plate compression. Resulting influx of sub-continental mantle
lithosphere (SCML) and asthenosphere provide a fertile metal source and heat, while the subducting slab contributes connate
and mineral dehydration fluids, which facilitate partial melting and metal leaching of SCML and asthenosphere. Cu–Au–Mo–(PGE)
porphyry deposits may develop where melts are trapped at shallow crustal levels, often with associated volcanism and epithermal-style
deposits (South Banat, Timok, and Panagyurishte). Mo–Fe–Pb–Zn skarn deposits may develop where felsic melts are trapped adjacent
to Mesozoic limestones at moderate crustal levels (North Banat and Apuseni). Systematic spatial variations in deposit style,
commodity enrichment, Re–Os ages, and Re concentrations support specific tectonic processes that led to ore formation. In
a post-collisional setting, subduction of Vardar oceanic crust may have stalled, causing slab steepening and rollback. The
slab rollback relaxes compression, facilitating and enhancing orogenic collapse of previously thickened Balkan-South Carpathian
crust. The progression of coupled rollback-orogenic collapse is evidenced by the width of Late Cretaceous extensional basins
and northward younging of Re–Os ages, from Panagyurishte (~60 km; 92–87 Ma) to Timok (~20 km; 88–81 Ma) to Apuseni-Banat (~5 km;
83–72 Ma). Generation of a well-endowed mineral belt, such as the ABTS, requires a temporally and spatially restricted window
of magmatic–hydrothermal activity. This window is quickly opened as upper plate compression relaxes, thereby inducing melt
generation and ingress of melt to higher crustal levels. The window is just as quickly closed as upper plate compression is
reinstated. The transient tectonic state responsible for economic mineralization in the ABTS belt may be a paleo-analogue
to transient intervals in the present subduction tectonics of SE Asia where much mineral wealth has been created in the last
few million years. 相似文献
10.
Ivica Vilibić Hrvoje Kalinić Hrvoje Mihanović Simone Cosoli Martina Tudor Nedjeljka žagar Blaž Jesenko 《Computational Geosciences》2016,20(1):115-131
We performed a number of sensitivity experiments by applying a mapping technique, self-organizing maps (SOM) method, to the surface current data measured by high-frequency (HF) radars in the northern Adriatic and surface winds modelled by two state-of-the-art mesoscale meteorological models, the Aladin (Aire Limitée Adaptation Dynamique Développement InterNational) and the Weather and Research Forecasting models. Surface current data used for the SOM training were collected during a period in which radar coverage was the highest: between February and November 2008. Different pre-processing techniques, such as removal of tides and low-pass filtering, were applied to the data in order to test the sensitivity of characteristic patterns and the connectivity between different SOM solutions. Topographic error did not exceed 15 %, indicating the applicability of the SOM method to the data. The largest difference has been obtained when comparing SOM patterns originating from unprocessed and low-pass filtered data. Introduction of modelled winds in joint SOM analyses stabilized the solutions, while sensitivity to wind forcing coming from the two different meteorological models was found to be small. Such a low sensitivity is considered to be favourable for creation of an operational ocean forecasting system based on neural networks, HF radar measurements and numerical weather prediction mesoscale models. 相似文献