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61.
Junxing Zheng Roman D. Hryciw Andrea Ventola 《Geotechnical and Geological Engineering》2017,35(5):2037-2051
This study quantifies the influence of various intrinsic soil properties including particle roundness, R, sphericity, S, 50% size by weight, D 50, coefficient of uniformity, C u, and the state property of relative density, D r, on the compression and recompression indices, C c and C r, of sands of various geologic origins at pre-crushing stress levels. Twenty-four sands exhibiting a wide range of particle shapes, gradations, and geologic origins were collected for the study. The particle shapes were determined using a computational geometry algorithm which allows characterization of a statistically large number of particles in specimens. One dimensional oedometer tests were performed on the soils. The new data was augmented with many previously published results. Through statistical analyses, simple functional relationships are developed for C c and C r. In both cases, the models utilized only R and D r since other intrinsic properties proved to have lesser direct influence on the compression indices. However, previous studies showed that the contributions of S and C u are felt through their effects on index packing void ratios and thus on D r. The accuracy of the models was confirmed by comparison of predicted and observed C c and C r values. 相似文献
62.
Filiz Bilgili Hans-Jürgen Götze Roman Pašteka Sabine Schmidt Ron Hackney 《International Journal of Earth Sciences》2009,98(3):571-583
An unsolved problem of regional importance for both the evolution and structure of the Northwest German Basin is the existence
or non-existence of the so-called Bramsche Massif. Explaining the nature of this massif and the cause of a related strong,
positive Bouguer anomaly (Bramsche Anomaly) is critical. In the study described here, we tested an existing “intrusion model”
against a newer “inversion model” in the southern Northwest German Basin. In the intrusion model, the strongly-positive Bouguer
anomaly represents the gravity effect of an intrusion at depths between 6 and 10 km. More recent interpretations invoke tectonic
inversion rather than intrusion to explain increased burial and the low level of hydrocarbon maturity found in boreholes.
We tested these different interpretations by constructing 3D forward density models to 15 km depth. The intrusion model was
updated and adjusted to incorporate recent data and we also modelled pre-Zechstein structures using different scenarios. The
final model has a very good fit between measured and modelled gravity fields. Based on currently available seismic and structural
models, as well as borehole density measurements, we show that the positive Bouguer anomaly cannot be modeled without a high-density,
intrusive-like body at depth. However, further in-sight into the crustal structures of the Bramsche region requires more detailed
investigations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
63.
Roman Teisseyre 《Acta Geophysica》2013,61(1):18-25
The Asymmetric Continuum Theory based on deformation fields includes the strain rotation as an equally important deformation part as the shear and confining strains; all these fields can be related to their origin in the fracture processes by some displacement motions in a source. Some of these motions may belong to an individual process, some to complex correlated events; in this latter case the displacements related to these strains could be shifted in phase. Moreover, we may expect an appearance of some molecular transport motions; the molecular transport may be helpful for understanding an interaction of the molecular processes and related molecular momentum flux. These correlated events should be mutually related in a source by the release-rebound mechanism. In particular, we consider the point fracture events as associated with a confining load or/and with the shear and rotation processes; we discuss the related effects and their meaning when discussing the fault plane mechanism and emitted waves. It is to be pointed out that such molecular motions are too small to be observed by the existing seismological networks. 相似文献
64.
Nicole Scheifhacken Ulrike Haase Lesya Gram-Radu Roman Kozovyi Thomas U. Berendonk 《Environmental Earth Sciences》2012,65(5):1483-1499
Recently, the Ukrainian Western Bug water authorities developed a national field survey to assess the quality of river habitats.
The Ukrainian government already cooperates with EU member states along transboundary rivers and also orientates itself towards
the European Water Framework Directive (WFD). As a future application for EU membership is feasible, the water authorities
started to implement WFD criteria into their national survey schemes including the assessment of rivers’ hydromorphology.
This article compares two different hydromorphological survey methods to identify similarities and differences of the classification
approaches with regard to the conformity of obtained outputs with the WFD demands. The field surveys, the Ukrainian (UA-FS)
and the German (LAWA-FS), were applied in parallel on 14 river sections along the Western Bug River and parts of its tributaries.
Results show a wide range of conformity, but also several differences between and gaps within all methods. The UA-FS generally
lacks the idea of reference condition in rivers’ hydromorphology and the definition of different stream types or near-natural
land uses. The UA-FS and the LAWA-FS approaches are similar with respect to their incorporated compartments and most main
parameters, but differ in definition and interpretation of specific functional units and single parameters. Greatest similarities
down to single parameters exist in aspects of land use, bank vegetation, currents diversity, and within-stream variation of
water depths. Differences include the assessment and interpretation of lateral erosion, sinuosity, type and depth of profile,
substrate diversity, as well as special structures of bank and riverbed. Overall, the LAWA-FS is more conservative in its
rating than the UA-FS. Still, UA-FS can be regarded as an important improvement for a systematic and reliable monitoring of
river hydromorphology in the Ukraine that will help to successfully engage with both the integrated water resources management
and the WFD harmonisation process in the future. 相似文献
65.
Roman Pevzner Valeriya Shulakova Anton Kepic Milovan Urosevic 《Geophysical Prospecting》2011,59(1):66-77
Time‐lapse seismics is the methodology of choice for remotely monitoring changes in oil/gas reservoir depletion, reservoir stimulation or CO2 sequestration, due to good sensitivity and resolving power at depths up to several kilometres. This method is now routinely applied offshore, however, the use of time‐lapse methodology onshore is relatively rare. The main reason for this is the relatively high cost of commercial seismic acquisition on land. A widespread belief of a relatively poor repeatability of land seismic data prevents rapid growth in the number of land time‐lapse surveys. Considering that CO2 sequestration on land is becoming a necessity, there is a great need to evaluate the feasibility of time‐lapse seismics for monitoring. Therefore, an understanding of the factors influencing repeatability of land seismics and evaluating limitations of the method is crucially important for its application in many CO2 sequestration projects. We analyse several repeated 2D and 3D surveys acquired within the Otway CO2 sequestration pilot project (operated by the Cooperative Research Centre for Greenhouse Technologies, CO2CRC) in Australia, in order to determine the principal limitations of land time‐lapse seismic repeatability and investigate the influence of the main factors affecting it. Our findings are that the intrinsic signal‐to‐noise ratio (S/N, signal to coherent and background noise levels) and the normalized‐root‐mean‐square (NRMS) difference are controlled by the source strength and source type. However, the post‐stack S/N ratio and corresponding NRMS residuals are controlled mainly by the data fold. For very high‐fold data, the source strength and source type are less critical. 相似文献
66.
Composition and origin of organic matter in surface sediments of Lake Sarbsko: A highly eutrophic and shallow coastal lake (northern Poland) 总被引:1,自引:0,他引:1
Micha? Woszczyk Achim Bechtel Reinhard Gratzer Maciej J. Kotarba Miko?aj Kokociński Jens Fiebig Roman Cie?liński 《Organic Geochemistry》2011,42(9):1025-1038
We present an organic geochemical study of surface sediments of Lake Sarbsko, a shallow coastal lake on the middle Polish Baltic coast. The aim was to provide evidence concerning the origin of the organic matter (OM) and its compositional diversity in surface deposits of this very productive, highly dynamic water body. The content and composition of the OM in the bottom sediments were investigated at 11 sampling stations throughout the lake basin. OM sources were assigned on the basis of bulk indicators [total organic carbon (TOC), total nitrogen (TN), δ13CTOC and δ15N and extractable OM yield], biomarker composition of extractable OM and compound-specific C isotope signatures. The source characterization of autochthonous compounds was verified via phytoplankton analysis. The distribution of gaseous hydrocarbons in the sediments, as well as temporal changes in lake water pH, the concentration of DIC (dissolved inorganic carbon) and δ13CDIC were used to trace OM decomposition.The sedimentary OM is composed mainly of well preserved phytoplankton compounds and shows minor spatial variability in composition. However, the presence of CH4 and CO2 in the bottom deposits provides evidence for microbial degradation of sedimentary OM. The transformation of organic compounds in surface, bottom and pore waters via oxidative processes influences carbonate equilibrium in the lake and seasonally favours precipitation or dissolution of CaCO3.The data enhance our understanding of the relationships between the composition of sedimentary OM and environmental conditions within coastal ecosystems and shed light on the reliability of OM proxies for environmental reconstruction of coastal lakes. 相似文献
67.
Hyon-Sohk Ohm Andhika Sahadewa Roman D. Hryciw Dimitrios Zekkos Nicholas Brant 《Geotechnical and Geological Engineering》2013,31(6):1647-1652
A rapid, clean, low-energy, image-based method for determining the grain size distribution of soils by image analysis has been developed. The method is called Sediment Imaging or “Sedimaging”. It develops the grain size distribution for particles in the range between a U.S. Standard Sieve No. 10 (2.0 mm openings) and U.S. Standard Sieve No. 200 (0.075 mm openings) range. The system utilizes a high resolution Nikon D7000 digital single lens reflex camera and image processing software developed specifically for interpreting the images and producing the resulting grain size distribution. The Sedimaging system is more sustainable and environmentally friendly than traditional sieving by virtue of its far lower power needs, less water consumption, longer equipment life and less maintenance. From the environmental and health perspectives, Sedimaging is less noisy, generates no vibrations and produces no airborne particulates. Sedimaging is also significantly faster than sieving and produces thousands of data points compared to typically 8 by sieving; it also automatically computes grain size distribution metrics such as the coefficients of uniformity and gradation. 相似文献
68.
We present a new development in the asymmetric continuum theory with the shear oscillations (twist motions) and independent
spin; these motions (displacement velocities and spin) can be shifted in phase to describe the independent rebound processes.
Our approach provides an extension of the asymmetric continuum theory by including the microfragmentation processes with a
double transport which may appear in an advanced fracture process under very high load. The related nonlinear equations, leading
to soliton solutions, are derived. 相似文献
69.
Charles T. Roman Norbert Jaworski Frederick T. Short Stuart Findlay R. Scott Warren 《Estuaries and Coasts》2000,23(6):743-764
Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estuaries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the domiant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure, function, and processes of estuaries along latitudinal gradients. 相似文献
70.