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21.
In this paper, the effect of soil disturbance caused by installation of prefabricated vertical drains (PVDs) on the rate of
consolidation is studied by two-dimensional finite element analysis. A transition zone lying between the highly disturbed
smear and the undisturbed zones is considered in the analysis. The hydraulic conductivity in the transition zone is assumed
to vary linearly from a low value in the smear zone to the original in situ value in the undisturbed zone. The analysis uses
the actual band shape of the PVD and the rectangular shape of the unit cell. A parametric study is carried out to investigate
the effects of the degree of soil disturbance, the size of the smear and the transition zones, the PVD spacing and the mandrel
size and shape. Design guidelines, where the smear and transition zones are replaced by an expanded smear zone producing the
same effect, are provided so that existing analytical solutions considering only the smear zone can be used for analysis and
design. A comparison with experimental results shows that consideration of the transition zone is important for correct estimation
of the degree of consolidation. 相似文献
22.
Swati Pralhadrao Deshmukh Bhagorao Tukaram Tate Nilkanth Dattatray Vagshette Sheo Kumar Pandey Madhav Khushalrao Patil 《天文和天体物理学研究(英文版)》2013,(8):885-898
We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6-7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ~ 2.13 105M⊙ . This is a lower limit compared to that estimated using the IRAS flux densities of ~5.17×106M⊙ and the flux densities at 24, 70 and 160 μm from MIPS ~3.2×107M⊙ . High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color-color plots for the resolved sources within the optical D 25 extent of NGC 1316 have enabled us to separate them into different classes. 相似文献
23.
Deformation analysis of soft ground reinforced by columnar inclusions 总被引:20,自引:0,他引:20
A simple theoretical approach to predict the deformation behaviour of soft ground reinforced by columnar inclusions such as stone columns./granular piles, sand compaction piles, lime or cement columns, etc., is presented in this paper. The analysis is performed based on the deformation properties of the column material and the surrounding soil. The interaction shear stresses between the column and the surrounding soil are considered to account for the stress transfer between the column and the soil. The solution is obtained by imposing compatibility between the displacements of the column and the soil for each element of the column-soil system. Numerical evaluations are made for a range of parameters to illustrate the influence of various parameters on the predictions. The proposed method is verified with finite element analysis and a reasonable agreement is obtained between the predictions. 相似文献
24.
Madhav L. Khandekar 《Natural Hazards》1994,9(1-2):125-153
The Grand Banks and the Scotian Shelf regions of the Canadian Atlantic often experience strong winds and high waves associated with the passage of intense storms during the winter months of December to March. These storm waves are identified as a major hazard to shipping, offshore exploration and other marine activities in eastern Canada.In this study, an operational spectral ocean wave model has been used to simulate sea-states associated with selected storm events in the Canadian Atlantic. The wave model operates on a grid (with grid spacing of about 111 km) which covers a major portion of the north Atlantic. A nested fine grid (with grid spacing of about 37 km) has been designed which covers the shelf regions of the Canadian Atlantic. The model employs deep-water physics over the coarse grid while over the fine grid shallow-water processes as represented by wave refraction, wave shoaling, bottom friction and wave number scaling are included. The wave model also includes, as an optional package, the third-generation source terms as represented by the nonlinear wave-wave interaction terms.For two selected storm events, the model generated sea-states are evaluated against available buoy data as well as against hand analyzed operational wave height charts over the northwest Atlantic. The evaluation shows that the various versions of the model can simulate the observed sea-states, reasonably well. The utility of the wave model in providing numerical guidance for offshore activities is briefly discussed. 相似文献
25.
Cyril Aubert Elodie Brisset Morteza Djamali Arash Sharifi Philippe Ponel Belinda Gambin Tayebeh Akbari Azirani Frédéric Guibal Hamid Lahijani Abdolmajid Naderi Beni Jacques-Louis de Beaulieu Ali Pourmand Valérie Andrieu-Ponel Alain Thiéry Emmanuel Gandouin 《Journal of Paleolimnology》2017,58(2):151-167
We reconstructed the paleohydrologic and climatic history of the Lake Neor region, NW Iran, from the end of the late glacial to the middle Holocene (15,500–7500 cal yr BP). Subfossil chironomid and pollen assemblages in a sediment core from a peatland located south of Lake Neor enabled identification of four main hydrologic phases. The period 15,500–12,700 cal yr BP was characterized by a relatively dry climate with an open landscape, suggested by the abundance of Irano-Turanian steppe plants (e.g. Amaranthaceae, Artemisia and Cousinia). Dominance of several shallow-water and semi-terrestrial chironomid taxa (e.g. Pseudosmittia, Smittia/Parasmittia and Paraphaenocladius/Parametriocnemus) during this period is indicative of lower water tables in the wetland. Between 12,700 and 11,300 cal yr BP, chironomid taxa indicate higher wetland water tables, as suggested by the presence of Zavrelia, Chironomus anthracinus/plumosus-type and Micropsectra, which are inhabitants of open-water, lacustrine areas. The open-steppe vegetation remained dominant in the watershed during this time. Increasing wetland moisture could be explained by: (1) cool summers that reduced the evaporation rate; and/or (2) a decrease in duration of the summer dry season. The period 11,300–8700 cal yr BP was characterized by lower wetland moisture, contemporaneous with a delay in the expansion of deciduous forest, suggesting persistent dry climate conditions throughout the beginning of the Holocene, which may have been related to the intensified seasonality of precipitation. Around 8700 cal yr BP, higher wetland water levels, inferred from chironomids, occurred simultaneously with the onset of regional deciduous forest expansion, probably caused by a shortening of the summer dry period. We concluded that chironomids are appropriate paleoecological proxies to investigate global and local hydrologic variability in the Middle East. 相似文献
26.
Stefano Branca Mauro Coltelli Emanuela De Beni Jan Wijbrans 《International Journal of Earth Sciences》2008,97(1):135-152
We present an updated geological evolution of Mount Etna volcano based on new 40Ar/39Ar age determinations and stratigraphic data integrating the previous K/Ar ages. Volcanism began at about 500 ka ago through
submarine eruptions on the Gela–Catania Foredeep basin. About 300 ka ago fissure-type eruptions occurred on the ancient alluvial
plain of the Simeto River forming a lava plateau. From about 220 ka ago the eruptive activity was localised mainly along the
Ionian coast where fissure-type eruptions built a shield volcano. Between 129 and 126 ka ago volcanism shifted westward toward
the central portion of the present volcano (Val Calanna–Moscarello area). Furthermore, scattered effusive eruptions on the
southern periphery of Etna edifice occurred until about 121 ka ago. The stabilization of the plumbing system on the Valle
del Bove area is marked by the building of two small polygenic edifices, Tarderia and Rocche volcanoes. Their eruptive activity
was rather coeval ending 106 and 102 ka ago, respectively. During the investigated time-span volcanism in Etna region was
controlled by a main E–W extensional tectonic related to the reactivation of Malta Escarpment fault system in eastern Sicily.
Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.
An erratum to this article can be found at 相似文献
27.
28.
Holger Class Anozie Ebigbo Rainer Helmig Helge K. Dahle Jan M. Nordbotten Michael A. Celia Pascal Audigane Melanie Darcis Jonathan Ennis-King Yaqing Fan Bernd Flemisch Sarah E. Gasda Min Jin Stefanie Krug Diane Labregere Ali Naderi Beni Rajesh J. Pawar Adil Sbai Sunil G. Thomas Laurent Trenty Lingli Wei 《Computational Geosciences》2009,13(4):409-434
29.
It is difficult to construct a conventional shallow foundation in alluvial lowlands because of soft soils and high ground
water table. A rigid short caisson foundation with granular core is being proposed for alluvial lowlands. The proposed foundation
is analyzed using non-linear hyperbolic stress–displacement responses of homogeneous alluvial deposits. Extensive parametric
studies are carried out to study the effects of length ratio (L/d0), diameter ratio (d/d0) of granular core with respect to casing, relative stiffness of shaft (ατ), relative casing base stiffness (αb), and friction angle of granular material (ϕgp) on the load sharing and the settlement of the proposed foundation. 相似文献
30.