Evaluation of Combined Direct-Push Methods Used for Aquifer Model Generation   总被引：4，自引：0，他引：4  

by Ralf Köber  Götz Hornbruch  Carsten Leven  Lars Tischer  Jochen Großmann  Peter Dietrich  Holger Weiß  Andreas Dahmke 《Ground water》2009,47(4):536-546

Most established methods to characterize aquifer structure and hydraulic conductivities of hydrostratigraphical units are not capable of delivering sufficient information in the spatial resolution that is desired for sophisticated numerical contaminant transport modeling and adapted remediation design. With hydraulic investigation methods based on the direct-push (DP) technology such as DP slug tests, DP injection logging, and the hydraulic profiling tool, it is possible to rapidly delineate hydrogeological structures and estimate their hydraulic conductivity in shallow unconsolidated aquifers without the need for wells. A combined application of these tools was used for the investigation of a contaminated German refinery site and for the setup of hydraulic aquifer models. The quality of DP investigation and the models was evaluated by comparisons of tracer transport simulations using these models and measured breakthroughs of two natural gradient tracer tests. Model scenarios considering the information of all tools together showed good reproduction of the measured breakthroughs, indicating the suitability of the approach and a minor impact of potential technical limitations. Using the DP slug tests alone yielded significantly higher deviations for the determined hydraulic conductivities compared to considering two or three of the tools. Realistic aquifer models developed on basis of such combined DP investigation approaches can help optimize remediation concepts or identify flow regimes for aquifers with a complex structure.  相似文献   

Wave-induced steady streaming,mass transport and net sediment transport in rough turbulent ocean bottom boundary layers   总被引：1，自引：0，他引：1  

Lars Erik Holmedal  Dag Myrhaug 《Continental Shelf Research》2009

The interaction between two important mechanisms which causes streaming has been investigated by numerical simulations of the seabed boundary layer beneath both sinusoidal waves and Stokes second order waves, as well as horizontally uniform bottom boundary layers with asymmetric forcing. These two mechanisms are streaming caused by turbulence asymmetry in successive wave half-cycles (beneath asymmetric forcing), and streaming caused by the presence of a vertical wave velocity within the seabed boundary layer as earlier explained by Longuet-Higgins. The effect of wave asymmetry, wave length to water depth ratio, and bottom roughness have been investigated for realistic physical situations. The streaming induced sediment dynamics near the ocean bottom has been investigated; both the resulting suspended load and bedload are presented. Finally, the mass transport (wave-averaged Lagrangian velocity) has been studied for a range of wave conditions. The streaming velocities beneath sinusoidal waves (Longuet-Higgins streaming) is always in the direction of wave propagation, while the streaming velocities in horizontally uniform boundary layers with asymmetric forcing are always negative. Thus the effect of asymmetry in second order Stokes waves is either to reduce the streaming velocity in the direction of wave propagation, or, for long waves relative to the water depth, to induce a streaming velocity against the direction of wave propagation. It appears that the Longuet-Higgins streaming decreases as the wave length increases for a given water depth, and the effect of wave asymmetry can dominate, leading to a steady streaming against the wave propagation. Furthermore, the asymmetry of second order Stokes waves reduces the mass transport (wave-averaged Lagrangian velocity) as compared with sinusoidal waves. The boundary layer streaming leads to a wave-averaged transport of suspended sediments and bedload in the direction of wave propagation.  相似文献   

Integration of GIS and Spatio-temporal Simulation Models: Interoperable Components for Different Simulation Strategies   总被引：1，自引：0，他引：1  

Lars Bernard  & Thomas Krüger 《Transactions in GIS》2000,4(3):197-215

New technologies for distributed object computing (DOC) challenge new approaches to integrate Geographical Information Systems (GIS) and simulation tools for spatio-temporal modeling. Several standardization initiatives work on specifying interfaces and defining service architectures for appropriate components. Currently, the most promising attempts are represented by the OpenGIS and the High Level Architecture. This paper gives a brief survey of the current state of the emerging standards, highlights the advantages and shortcomings of these attempts, and defines a possible framework for GIS-integrated simulation of spatio-temporal processes. Two abstraction layers provide interfaces for different GIS kernels and allow the integration of different simulation models. A prototype implementation of the specified interfaces shows the integration of analysis tools and two different simulation strategies: a mesoscale boundary layer model based on the Navier-Stokes equation and a cellular automata to simulate air pollutant dispersion.  相似文献   

The atmospheric geoid effects in Stokes' formula   总被引：2，自引：0，他引：2  

Lars E. Sjöberg  & Hossein Nahavandchi 《Geophysical Journal International》2000,140(1):95-100

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New interglacial deposits from Copenhagen,Denmark: marine Isotope Stage 7     

Ole Bennike  Lars Hedens  Kirsty High  Joakim S. Korshj  Geoffrey Lemdahl  Kirsty Penkman  Richard C. Preece  Knud Rosenlund  Finn A. Viehberg 《Boreas: An International Journal of Quaternary Research》2019,48(1):107-118

During a pre‐site survey and construction of a new metro route and station in Copenhagen, fossiliferous organic‐rich sediments were encountered. This paper reports on multidisciplinary investigations of these organic sediments, which occurred beneath a sediment succession with a lower till, glacifluvial sand and gravel, an upper till and glacifluvial sand. The organic sediments were underlain by glacifluvial sand and gravel. The organic‐rich sediments, which were up to 0.5 m thick, accumulated in a low‐energy environment, possibly an oxbow lake. They were rich in plant fossils, which included warmth‐demanding trees and other species, such as Najas minor, indicating slightly higher summer temperatures than at present. Freshwater shells were also frequent. Bithynia opercula allowed the sediments to be put into an aminostratigraphical framework. The amino acid racemization (AAR) ratios indicate that the organic sediments formed during Marine Isotope Stage 7 (MIS 7), which is consistent with optically stimulated luminescence dating that gave ages of 206 and 248 ka from the underlying minerogenic deposit. The assemblages from Trianglen are similar to interglacial deposits from the former Free Port (1.4 km away) in Copenhagen, except that Corbicula and Pisidium clessini were not found at Trianglen. The presence of these bivalves at the Free Port and the ostracod Scottia tumida at Trianglen indicates a pre‐Eemian age. AAR data from archived Bithynia opercula from the Free Port were almost identical to those from Trianglen, indicating that the two sites are contemporary. We suggest the Trianglen interglacial be used as a local name for the MIS 7 interglacial deposits in Copenhagen. MIS 7 deposits have rarely been documented from the region, but MIS 7 deposits may have been mistaken for other ages. The use of AAR ratios in Bithynia opercula has a great potential for correlation of interglacial non‐marine deposits in mainland northern Europe.  相似文献   

Frequency locking in a periodically forced thermal two-phase oscillator     

Peter Lundberg  Lars Rahm 《Dynamics of Atmospheres and Oceans》1984,8(1):59-72

Welander (1977) showed that a fluid, heated internally and cooled to freezing from above, can for a certain parameter range and for steady thermal forcing demonstrate oscillatory behaviour with ice-covered and ice-free states alternating. This concept has been extended to encompass the geophysically important case of cyclic cooling. Numerical investigations have revealed that periodically forced either shows frequency locking or quasiperiodic behaviour.  相似文献   

New method of quantitatively describing drainage areas     

Lars HÅkanson  Tord Andersson  Ake Nilsson 《Environmental Geology》1990,15(1):61-69

The aim was to introduce a new method, the DAZ method (drainage area zonation), to quantify environmental parameters, such as bedrocks, soil type, and land use in drainage areas. The work was carried out within the framework of the Swedish project Liming—mercury. Two important points in the project are that there are quantifiable relationships between the character of the drainage area and the lake and that several limnological and morphometric parameters may have an impact on the Hg content in fish. The DAZ method accounts for the fact that, for example, a certain soil type does not have an even distribution in the whole drainage area. To get a simple yet relevant measure of the influence of, for example, soil type on the lake character, the drainage areas were divided into zones using a special transparent paper placed on the map. The method gives normalized values depending on: (1) distance between the object and the given lake, (2) the main direction of water flow in the drainage area, and (3) the area of the environmental parameter (for example, area of bedrock). In the DAZ method, dot counting is used for determination of area. The dot-counting method has been compared with other methods for area determination (planimeter and square counting). Dot counting is the fastest and the counting of squares the most time consuming. The statistical reliabilities of the dot method and the planimeter method were compared. The planimeter is best for large homogeneous objects. Dot counting, on the other hand, is very well suited for heterogeneous objects. The statistical certainty of area determination depends on size, heterogeneity, and form of the objects, as well as the time dedicated to the determination. A nomogram is also given, which illustrates the relationship between the number of counts, that is, the number of times the transparent dotted paper is put on the map and the dots counted, the error in the area determination, and the statistical reliability.  相似文献   

Provenance of the Lower Triassic Bunter Sandstone Formation: implications for distribution and architecture of aeolian vs. fluvial reservoirs in the North German Basin          下载免费PDF全文

Mette Olivarius  Rikke Weibel  Henrik Friis  Lars O. Boldreel  Nynke Keulen  Tonny B. Thomsen 《Basin Research》2017,29(Z1):113-130

Zircon U–Pb geochronometry, heavy mineral analyses and conventional seismic reflection data were used to interpret the provenance of the Lower Triassic Bunter Sandstone Formation. The succession was sampled in five Danish wells in the northern part of the North German Basin. The results show that sediment supply was mainly derived from the Ringkøbing‐Fyn High situated north of the basin and from the Variscan belt located south of the basin. Seismic reflection data document that the Ringkøbing‐Fyn High was a local barrier for sediment transport during the Early Triassic. Hence, the Fennoscandian Shield did not supply much sediment to the basin as opposed to what was previously believed. Sediment from the Variscan belt was transported by wind activity across the North German Basin when it was dried out during deposition of the aeolian part of the Volpriehausen Member (lower Bunter Sandstone). Fluvial sand was supplied from the Ringkøbing‐Fyn High to the basin during precipitation events which occurred most frequently when the Solling Member was deposited (upper Bunter Sandstone). Late Neoproterozoic to Carboniferous zircon ages predominate in the Volpriehausen Member where the dominant age population with a peak age of 337 Ma corresponds to the culmination of Variscan high‐grade metamorphism, whereas a secondary age population with a peak at 300 Ma matches the timing of volcanism and magmatism at the Carboniferous/Permian boundary in the northern Variscan belt. Parts of the basement in the Ringkøbing‐Fyn High were outcropping during the Early Triassic and zircon ages similar to this Mesoproterozoic basement are present in the Bunter Sandstone. The heavy mineral assemblage of the Solling Member is uniform and has a high garnet content compared to the contemporaneous sediments in the Norwegian‐Danish Basin and in the southern part of the North German Basin. This finding confirms that a local source in the Ringkøbing‐Fyn High supplied most of the fluvial sediment in the northern part of the North German Basin. The northernmost part of the Bunter Sandstone is situated on a platform area that is separated from the basin area by a broad WNW–ESE‐oriented fault zone. The most promising reservoir in the basin area is the aeolian Volpriehausen Member since the sandstone has a wide lateral distribution and a constant thickness. The alluvial to ephemeral fluvial Solling Member may be a good reservoir in the platform area and marginal basin area, but the complex sand‐body architecture makes it difficult to predict the reservoir quality.  相似文献   

Åland GPS levelling campaign in 1987     

Lars E. Sjöberg 《Journal of Geodesy》1991,65(4):209-217

In October 1987 a four day satellite GPS campaign was performed over the Åland archipelago to test the possibility of connecting the Swedish and Finnish national height systems. This paper summarizes the gained experiences using 5 WM 101 GPS receivers and the PoPS software.The computing results for the connection between the two height systems are considerably dependent on the choice of geoidal undulation model and systematic error parameter model. Using the NKG Scandinavian geoid 1989, which is probably the most accurate geoid available for the region, and a bias and tilt parameter model the difference between the Swedish RH70 system and the Finnish N60 system is estimated to 11.4 ± 4.0 cm. An independent check is provided by two connecting border bench marks in northern Scandinavia yielding the difference 19.2 ± 4.2 cm. In view of that merely single frequency GPS receivers were used together with the PoPS software, we consider this result most satisfactory.  相似文献   

Common Sense in Ground-Water Protection and Management in the United States     

Harry E. LeGrand  Lars Rosen 《Ground water》1992,30(6):867-872

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