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51.
John F. Hiemstra Bernd Kulessa Edward C. King Dimitris Ntarlagiannis 《地球表面变化过程与地形》2011,36(14):1860-1871
Despite significant advances over the past decades, our understanding of drumlin formation and associated ice‐bed processes is still incomplete. In this paper, we present the integrated use of geomorphological, sedimentological and geophysical techniques as a powerful means to force a breakthrough towards solving the drumlin enigma. We report on investigations of the anatomy of the Pigeon Point drumlin, Clew Bay, Ireland. We found that the bulk of the landform, which displays a classical drumlin shape, consists of silty‐clayey diamicton showing evidence of deformation, hydrofracturing and comminution. The unit is interpreted as a sub‐glacial traction till/comminution till. The thin unit overlying this basal till consists of silty‐sandy diamicton, and is interpreted as a para‐glacially modified melt‐out till. The partly cemented third unit consists of stratified, massive to graded sands and gravels. Its contact with the sub‐glacial traction till consists of a series of concave shapes, which suggests that it was deposited in meltwater channels that flowed in sub‐glacial cavities and that cut laterally into the drumlin. We propose that highs in the undulating rockhead relief, as shown in the seismic profile, have provided nuclei which initiated drumlin formation. This idea is supported by the observation of local detached bedrock slabs that grade upwards into a comminution till. In the long profile, very high normalized induced polarization (IP) values form a wedge‐shape, which is interpreted as a set of conjugate thrusts, or a ‘pop‐up’ structure. The structure is positioned directly above one of the undulations in the bedrock, suggesting a direct relationship. The high values are thought to reflect the presence of pre‐existing clays, which were sheared into the till, thus forming linings in the thrust features. It is concluded that glacitectonic processes, notably differential bedrock weathering and thrusting, have played a key role in the formation of this drumlin. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
52.
Dimitris Papadopoulos Michael Herty Volker Rath Marek Behr 《Computational Geosciences》2011,15(4):737-753
A shape reconstruction method for geophysical objects by temperature measurements is presented which uses adjoint equations
and a level set function approach. Temperature is measured on subdomains, e.g., representing boreholes. This information is
used to reconstruct the shape of the geophysical layers. For this purpose, shape optimization techniques are applied. The
method uses a representation of the layers by a so-called level set function. The evolution of this level set function is
then used to determine the optimal shape. The “speed” of the evolution is computed using adjoint equations. Synthetic examples
demonstrate the use of the inverse method and its behavior in different configurations. 相似文献
53.
Dimitris Alexakis Dimitris Gotsis Spyros Giakoumakis 《Arabian Journal of Geosciences》2015,8(3):1373-1383
Soil salinization is an environmental problem having significant impacts on the soil–water–plant system. This problem is more frequent in coastal areas due to seawater intrusion into the land. Assessing the soil salinization is a critical issue for the agricultural areas situated in the Mediterranean basin. This paper examines the deterioration of soil quality in the cultivated land of a Mediterranean site (Agoulinitsa district—West Greece). Soil samples were collected in both pre-irrigation and post-irrigation seasons. Electrical conductivity (EC), pH and the ions Br?, Ca2+, Cl?, F?, K+, Li+, Mg2+, Na+, NH4 +, NO2 ?, NO3 ?, PO4 3? and SO4 2? were determined by the 1:2 (soil/water ratio on weight basis) method. The salts which were present in both seasons in the soils of the area studied are KCl, MgCl2, NaCl, CaSO4 and K2SO4. The wide spatiotemporal variation of EC in the cultivated land in both seasons demonstrates that soil salinity is controlled mainly by seawater intrusion and anthropogenic factors such as the application of salt-rich water which is directly pumped from the drainage ditches. Seawater intrusion provides the affected soil with elevated contents of Ca2+, Cl?, K+, Mg2+, Na+ and SO4 2?. Classification of the soils by using criteria given by the literature is discussed. Practices to prevent, or at least ameliorate, salinization in the cultivated land of Agoulinitsa district are proposed. 相似文献
54.
I. Lagiopoulos A. Binteris Τ. Mpouras I. Panagiotakis M. Chrysochoou D. Dermatas 《International Journal of Environmental Science and Technology》2017,14(7):1481-1488
The present study reports on the preliminary investigation of three low-cost natural materials with respect to their chromium(VI) removal efficiency from contaminated water. The tested materials were reed, in milled and chopped form, compost, and dewatered sludge from a municipal wastewater treatment plant. The chromium(VI) removal capacity of the aforementioned materials was investigated by simulating the physicochemical conditions prevailing in a stormwater outfall flowing into the Asopos River in Inofyta, Central Greece. Thus, batch and column experiments were carried out using solutions of 3–5 mg/L chromium(VI) and pH value 8.5 ± 0.5. The results showed that the tested materials were capable of removing 3 mg/L chromium(VI), however by allowing different contact times for each material. The chromium(VI) removal kinetics were studied through batch experiments, and reed was found to be the most efficient material. Therefore, at a second series of batch and up-flow column experiments, the effect of the liquid-to-solid ratio, pH, and contact time on chromium(VI) removal using chopped reed was investigated. Chromium(VI) removal took place through both reduction and adsorption mechanisms, while the released soluble organic matter from reed seemed to favor the reduction mechanism. As a result, reed is a potential biosorbent capable of treating heavily chromium(VI)-contaminated water flows, although a high mass of reed is required for a treatment process, such in the case of the stormwater discharged into Asopos River. 相似文献
55.
During the last decades legislative actions on environmental issues have dramatically increased all over the world. The impacts of environmental legislation on the mining sector are quite significant. Although an extensive list of legislation exists, this paper focuses on an issue that currently has a significant influence on the mining industry: natural resource damage assessment and, in particular, the valuation of non-market goods. Therefore, the basic elements of the most important valuation methods are outlined and a demonstrative example is presented, in the context of appraising a reclamation scheme of an abandoned quarry site. The analysis is fairly general, and it does not intend to comprise either a complete introduction to environmental economics or a comprehensive presentation of valuation techniques. Still, it provides an idea of how these methods can be applied to mining issues. Further, the findings may prove useful to practitioners and mining managers, providing information about the monetary benefits of mined land reclamation that could contribute to sound decision- and policy-making. 相似文献
56.
Edward H. Stehmeyer III Dimitris C. Rizos 《Soil Dynamics and Earthquake Engineering》2006,26(5):421-434
This work presents a simplified, yet accurate model of rigid foundation-soil systems for the dynamic analysis of structures including SSI effects. The simplified model is based on closed form solutions that reproduce the characteristic B-spline impulse response functions (BIRF) of 3D continuous soil-foundation systems, as obtained from rigorous boundary element method (BEM) analysis. The proposed simplified model is used within the framework of B-spline impulse response techniques and can be coupled directly to other solution techniques, such as the finite element method (FEM). Validation and application studies demonstrate the accuracy and versatility of the simplified model for the direct time domain solution of dynamic SSI problems involving rigid square surface foundations of any size. The proposed model, although simplified, demonstrates similar high accuracy to that of more rigorous solutions based on domain discretizations. 相似文献
57.
Tomoki Nakaya A. Stewart Fotheringham Kazumasa Hanaoka Graham Clarke Dimitris Ballas Keiji Yano 《Journal of Geographical Systems》2007,9(4):345-369
Although the disaggregation of consumers is crucial in understanding the fragmented markets that are dominant in many developed
countries, it is not always straightforward to carry out such disaggregation within conventional retail modelling frameworks
due to the limitations of data. In particular, consumer grouping based on sampled data is not assured to link with the other
statistics that are vital in estimating sampling biases and missing variables in the sampling survey. To overcome this difficulty,
we propose a useful combination of spatial interaction modelling and microsimulation approaches for the reliable estimation
of retail interactions based on a sample survey of consumer behaviour being linked with other areal statistics. We demonstrate
this approach by building an operational retail interaction model to estimate expenditure flows from households to retail
stores in a local city in Japan, Kusatsu City.
相似文献
58.
Francisco J. Chávez-García Francisco Luzón Dimitris Raptakis José Fernández 《Pure and Applied Geophysics》2007,164(4):697-720
Deformation analysis and simulation of volcanic edifices require the construction of models of elastic properties of those
structures. In this paper we present an analysis of microtremor measurements recorded during the performance tests of two
temporary seismic arrays installed in the eastern portion of the Teide caldera in 1994. We take advantage of recent developments
of the SPAC method and use spatial cross-correlation computations to estimate phase velocity dispersion of Rayleigh waves
at the location of the arrays. We show that the extension of the standard SPAC method is valid in the case of our data, justifying
its use and supporting the generalization of the SPAC method to single station pairs. The phase velocity dispersion curve
obtained was inverted to recover the shear-wave profile at the site of the arrays. Our results indicate that the subsoil structure
of the caldera is laterally homogeneous at the scale of a few km about the location of the arrays. We obtained about 315 m
of volcanic sediments overlying rocks with a shear-wave velocity of 2 km/s. These results are robust and are a starting point
to further modelling of deformation, permanent or transient, at this volcanic edifice, which can be useful in the interpretation
of different observed fields. In fact, the computation of deformations and gravity changes due to possible volcanic intrusions
in two models; one considering the volcanic sediments and the other without considering them, provided different results in
the near field. 相似文献
59.
In this work the interaction between adjacent rigid, surface foundations resting on a viscoelastic layered soil medium is studied. A 3-D frequency domain BEM formulation in conjunction with infinite space fundamental solutions and the so called `successive stiffness method', initially developed for elastostatics and adapted here for the solution of elastodynamic problems, are used for the simulation of a layered soil medium. As a result, a discretization of the soil-foundation interface and the surrounding free surface as well as the soil layers' interfaces is necessary. However, it is shown in this work that reasonably accurate results can be obtained by using a substantially reduced discretization scheme involving only a small portion of the free surface surrounding the foundation and the corresponding interfaces of the soil layers. The presented numerical results demonstrate the importance of the dynamic foundation-soil-foundation interaction phenomenon which becomes even more pronounced where the supporting soil medium is made up of relatively shallow layers close to its free surface. 相似文献
60.
A number of different methods for the 3D measurement of the water surface in wave fields have been proposed in the literature, based mostly on refraction, photogrammetry and/or reflected light intensity. Although these methods can map the distorted water surface, they appear to be difficult in practical applications in hydraulic engineering laboratories. A novel wave mapping technique using particle image velocimetry to measure surface flow velocities, and linear wave theory to determine wave heights from the measured velocities, has been developed and validated for regular waves. The method allows for the mapping even of complex wave fields with simple means and appears robust enough for application in the laboratory. 相似文献