Simulation of groundwater drainage into a tunnel in fractured rock and numerical analysis of leakage remediation, Romeriksporten tunnel, Norway   总被引：1，自引：1，他引：0  

N.-O. Kitterød  H. Colleuille  W. Wong  T. Pedersen 《Hydrogeology Journal》2000,8(5):480-493

Standard geostatistical methods for simulation of heterogeneity were applied to the Romeriksporten tunnel in Norway, where water was leaking through high-permeable fracture zones into the tunnel while it was under construction, causing drainage problems on the surface. After the tunnel was completed, artificial infiltration of water into wells drilled from the tunnel was implemented to control the leakage. Synthetic heterogeneity was generated at a scale sufficiently small to simulate the effects of remedial actions that were proposed to control the leakage. The flow field depends on the variance of permeabilities and the covariance model used to generate the heterogeneity. Flow channeling is the most important flow mechanism if the variance of the permeability field is large compared to the expected value. This condition makes the tunnel leakage difficult to control. The main effects of permeability changes due to sealing injection are simulated by a simple perturbation of the log-normal probability density function of the permeability. If flow channeling is the major transport mechanism of water into the tunnel, implementation of artificial infiltration of water to control the leakage requires previous chemical-sealing injection to be successful. Electronic Publication  相似文献   

Removal of DC power-line magnetic-field effects from airborne total magnetic-field measurements     

Mehran Gharibi  & Laust B. Pedersen 《Geophysical Prospecting》2000,48(3):617-627

Power lines carrying DC current can strongly affect total magnetic-field measurements. A simple algorithm using Biot–Savart's law was made to remove magnetic-field components due to a DC power line from airborne total magnetic-field measurements in the Gävle area, Sweden. The power-line location was estimated from observed data and then split into short line segments. The magnetic-field components due to each segment were calculated and summed together to give the total magnetic effect due to the power line at each observation point. The corrected total magnetic field was calculated by subtracting the power-line magnetic-field vector, projected on to the direction of the main field, from the measured total field. The results show a successful removal of the power-line magnetic effect from the total magnetic-field measurements. However, an error in the estimation of the power-line location can result in a magnetic-field residual after correction. A non-linear median filtering was used to remove this residual when needed.  相似文献   

Assessing the Transport of Pharmaceutical Compounds in a Layered Aquifer Discharging to a Stream     

Nicola Balbarini  Majken Frederiksen  Vinni Rønde  Ingelise Møller  Anne T. Sonne  Ursula S. McKnight  Jørn K. Pedersen  Philip J. Binning  Poul L. Bjerg 《Ground water》2020,58(2):208-223

A groundwater plume containing high concentrations of pharmaceutical compounds, mainly sulfonamides, barbiturates, and ethyl urethane, in addition to chlorinated ethenes and benzene was investigated. The contamination originating from a former pharmaceutical industry discharges into a multilayered aquifer system and a downgradient stream. In this study, geological and hydrogeological data were integrated into a numerical flow model to examine identified trends using statistical approaches, including principal component analysis and hierarchal cluster analysis. A joint interpretation of the groundwater flow paths and contaminant concentrations in the different compartments (i.e., groundwater and hyporheic zone) provided insight on the transport processes of the different contaminant plumes to the stream. The analysis of historical groundwater concentrations of pharmaceutical compounds at the site suggested these compounds are slowly degrading. The pharmaceutical compounds migrate in both a deep semiconfined aquifer, as well as in the shallow unconfined aquifer, and enter the stream along a 2-km stretch. This contrasted with the chlorinated ethenes, which mainly discharge to the stream as a focused plume from the unconfined aquifer. The integrated approach developed here, combining groundwater flow modeling and statistical analyses of the contaminant concentration data collected in groundwater and the hyporheic zone, lead to an improved understanding of the observed distribution of contaminants in the unconfined and semiconfined aquifers, and thus to their discharge to the stream. This approach is particularly relevant for large and long-lasting contaminant sources and plumes, such as abandoned landfills and industrial production sites, where field investigations may be very expensive.  相似文献   

Three‐dimensional modelling of magnetotelluric data to image Sehqanat hydrocarbon reservoir in southwestern Iran          下载免费PDF全文

I. Mansoori  L.B. Pedersen  R. Javaheri 《Geophysical Prospecting》2016,64(3):753-766

A detailed magnetotelluric survey was conducted in 2013 in the Sehqanat oil field, southwestern Iran to map the geoelectrical structures of the sedimentary Zagros zone, particularly the boundary between the Gachsaran Formation acting as cap rock and the Asmari Formation as the reservoir. According to the electrical well logs, a large resistivity contrast exists between the two formations. The Gachsaran Formation is formed by tens to hundreds of metres of evaporites and it is highly conductive (ca. 1 Ωm–10 Ωm), and the Asmari Formation consists of dense carbonates, which are considerably more resistive (more than 100 Ωm). Broadband magnetotelluric data were collected along five southwest–northeast directed parallel lines with more than 600 stations crossing the main geological trend. Although dimensionality and strike analysis of the magnetotelluric transfer functions showed that overall they satisfied local 2D conditions, there were also strong 3D conditions found in some of the sites. Therefore, in order to obtain a more reliable image of the resistivity distribution in the Sehqanat oil field, in addition to standard 2D inversion, we investigated to what extent 3D inversion of the data was feasible and what improvements in the resistivity image could be obtained. The 2D inversion models using the determinant average of the impedance tensor depict the main resistivity structures well, whereas the estimated 3D model shows significantly more details although problems were encountered in fitting the data with the latter. Both approaches resolved the Gachsaran–Asmari transition from high conductivity to moderate conductivity. The well‐known Sehqanat anticline could also be delineated throughout the 2D and 3D resistivity models as a resistive dome‐shaped body in the middle parts of the magnetotelluric profiles.  相似文献   

Decision bias in marine spatial planning of offshore wind farms: Problems of singular versus cumulative assessments of economic impacts on fisheries     

Jörg Berkenhagen  Ralf Döring  Heino O. Fock  Matthias H.F. Kloppmann  Søren A. Pedersen  Torsten Schulze 《Marine Policy》2010

The current approval procedure for wind farm proposals in the German EEZ only considers site specific conflict analysis between the wind farm and fisheries. Due to the relatively small spatial coverage of the sites potential opportunity losses to the fisheries are always considered as low or negligible. Cumulative effects on fisheries that will occur once all proposed wind farms are in place are not yet considered adequately. However, those cumulative effects will be quite substantial because, in particular, opportunities to catch such valuable species as flatfish will be considerably reduced.  相似文献   

Experimental investigation of impact generated tsunami; related to a potential rock slide,Western Norway     

G. Sælevik  A. JensenG. Pedersen 《Coastal Engineering》2009

Two-dimensional experiments of wave generation from the possible Åkneset rock slide have been performed using solid block modules in a transect with a geometric scaling factor of 1:500. The width of the slide model was kept fixed at 0.45 m. The length of the blocks spanned from 1 to 2 m, the thickness was either 0.12 or 0.16 m and the front angle was 45°. Maximum water depth was 0.6 m with the slide plane having an angle of 35°. Three different scenarios were studied. Only the run out side was modelled.  相似文献   

The constrained politics of the Svalbard offshore area     

Torbjrn Pedersen 《Marine Policy》2008,32(6):913-919

This study identifies some mechanisms through which external factors constrain state behavior. Examining Norwegian governance for the disputed Svalbard offshore area, it finds the behavior of Norway to be constrained in multiple ways by the conflicting policies of foreign powers toward the area. When shaping the management regime of the controversial maritime zones of the former terra nullius Svalbard, Norwegian authorities cautiously consider the possible international ramifications of their actions. Norway's behavior—not only manifested in policy but also in the exercise of contested legislative and enforcement jurisdiction—is curbed amid international disagreements over Norwegian rights in the area.  相似文献   

Holocene evolution of a drowned melt-water valley in the Danish Wadden Sea     

Jørn B.T. Pedersen  Steffen Svinth 《Quaternary Research》2009,72(1):68-104

Cores from the salt marshes along the drowned melt-water valley of river Varde Å in the Danish Wadden Sea have been dated and analysed (litho- and biostratigraphically) to reconstruct the Holocene geomorphologic evolution and relative sea level history of the area. The analysed cores cover the total post-glacial transgression, and the reconstructed sea level curve represents the first unbroken curve of this kind from the Danish Wadden Sea, including all phases from the time where sea level first reached the Pleistocene substrate of the area. The sea level has been rising from − 12 m below the present level at c. 8400 cal yr BP, interrupted by two minor drops of < 0.5 m at c. 5500 cal yr BP and 1200 cal yr BP, and one major drop of ∼ 1.5 m at c. 3300 cal yr BP. Sediment deposition has been able to keep pace with sea level rise, and the Holocene sequence consists in most places of clay atop a basal peat unit overlying sand of Weichselian age and glacio-fluvial origin. In its deepest part, the basal peat started to form around 8400 cal yr BP, and reached a thickness of up to 3.5 m. This thickness is about half of the original, when corrected for auto-compaction. The superimposed clay contains small (63-355 μm) red iron stains in the top and bottom units, and foraminifers of the calcareous type in the middle. The fact that iron stains and foraminifers in no cases coexist, but always exclude each other is interpreted as a result of the difference between salt-marsh facies (iron stains) and tidal-flat facies (foraminifers). This represents a novel and easy way to distinguish between these two otherwise often undistinguishable sedimentary facies in the geological record.  相似文献   

The 1732 Surtseyan eruption of Eggøya,Jan Mayen,North Atlantic: deposits,distribution, chemistry and chronology     

Eirik Gjerløw  Armann Höskuldsson  Rolf-Birger Pedersen 《Bulletin of Volcanology》2015,77(2):1-21

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Characterization of soil organic carbon in drained thaw-lake basins of Arctic Alaska using NMR and FTIR photoacoustic spectroscopy   总被引：2，自引：0，他引：2  

Joel A. Pedersen  Myrna A. SimpsonJames G. Bockheim  Kartik Kumar 《Organic Geochemistry》2011,42(8):947-954

Arctic soils contain a large fraction of Earth’s stored carbon. Temperature increases in the Arctic may enhance decomposition of this stored carbon, shifting the role of Arctic soils from a net sink to a new source of atmospheric CO₂. Predicting the impact of Arctic warming on soil carbon reserves requires knowledge of the composition of the stored organic matter. Here, we employ solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) to investigate the chemical composition of soil organic matter collected from drained thaw-lake basins ranging in age from 0 to 5500 years before present (y BP). The ¹³C NMR and FTIR-PAS data were largely congruent. Surface horizons contain relatively large amounts of O-alkyl carbon, suggesting that the soil organic matter is rich in labile constituents. Soil organic matter decreases with depth with the relative amounts of O-alkyl carbon decreasing and aromatic carbon increasing. These data indicate that lower horizons are in a more advanced stage of decomposition than upper horizons. Nonetheless, a substantial fraction of carbon in lower horizons, even for ancient thaw-lake basins (2000-5500 y BP), is present as O-alkyl carbon reflecting the preservation of intrinsically labile organic matter constituents. Climate change-induced increases in the depth of the soil active layer are expected to accelerate the depletion of this carbon.  相似文献