Mechanical behavior of silty soils of the Venice lagoon as a function of their grading characteristics

2002 ◽  
Vol 39 (4) ◽  
pp. 879-893 ◽  
Author(s):  
Simonetta Cola ◽  
Paolo Simonini
Keyword(s):  
Grain Size ◽  
Mechanical Behavior ◽  
Laboratory Investigation ◽  
Venice Lagoon ◽  
Soil Response ◽  
Regular Trend ◽  
Size Index ◽  
Geological Origin ◽  
Silty Soils ◽  
Historic City

The main feature of the shallowest quaternary basin of the well-renowned historic city of Venice, Italy and its surrounding lagoon, is the presence, apparently without any regular trend in depth and site, of a predominant silt fraction. This is always combined with clay and (or) sand, forming a chaotic and erratic interbedding of different sediments whose mineralogy is however variable in a relatively narrow range due to a unique geological origin and a common depositional environment. After a brief description of the basic soil indexes of the Venice lagoon soil, the present study, based on a comprehensive geotechnical laboratory investigation, describes the range of variation of the most relevant time-independent geotechnical properties. Moreover, a new grain size index, combining the geometrical characteristics of the particle distribution, is introduced. It is shown that the soil response at large and very small strains can be related to this grain size index, which appears to be able to include the influence of the soil grading on the description of the overall mechanical behavior.Key words: silt, mechanical behavior, Venice soil, grain-size index, laboratory investigation, critical state parameters.

Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

2002 ◽  
Vol 17 (1) ◽  
pp. 5-8 ◽  
Author(s):  
R. Z. Valiev ◽  
I. V. Alexandrov ◽  
Y. T. Zhu ◽  
T. C. Lowe
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Yield Strength ◽  
Mechanical Behavior ◽  
High Strength ◽  
High Ductility ◽  
Elongation To Failure ◽  
Failure Ductility ◽  
Strength And Ductility

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.

The impact of Dansgaard–Oeschger cycles on the loessic environment and malacofauna of Nussloch (Germany) during the Upper Weichselian

2008 ◽  
Vol 70 (1) ◽  
pp. 91-104 ◽  
Author(s):  
Olivier Moine ◽  
Denis-Didier Rousseau ◽  
Pierre Antoine
Keyword(s):  
Grain Size ◽  
Environmental Changes ◽  
Ice Core ◽  
Schematic Model ◽  
Climatic Fluctuations ◽  
Climatic Oscillations ◽  
The North ◽  
Size Index ◽  
The Impact ◽  
Hygrophilous Species

AbstractA loess sequence has been sampled continuously at high resolution in Nussloch (Rhine Valley, Germany) for malacological and grain-size analyses between ca. 34 and 20 ka. Molluscan abundance and richness, percentage in hygrophilous species and grain-size index show cyclical variations related to the lithological loess–gley alternation. Major molluscan abundance maxima were triggered by temperature increases through an enhancement of the reproduction cycle, whereas cyclical richness fluctuations and percentage in hygrophilous species reflect variations in local humidity and changes in the environmental mosaic. Malacological parameters allow the distinction of four environmental phases organised in cyclical successions correlated with most of the loess–gley doublets. The correlation of the grain-size index of the Nussloch loess sequence with the dust content of the GRIP ice core demonstrates the synchronicity of major molluscan abundance maxima and δ18O increases characterising temperature increases during Dansgaard–Oeschger interstades. A schematic model is proposed to link the North Atlantic Dansgaard–Oeschger climatic oscillations with local environmental changes indicated by both malacofauna and pedostratigraphy. This malacological study of the Nussloch loess sequence thus provides new information about the response of terrestrial loessic palaeoenvironments to millennial-timescale climatic fluctuations during the Upper Weichselian (∼ marine isotope stage 2 (MIS 2) and end of MIS 3).

Laboratory investigation of dune erosion as a function of sand grain size and dune density

1994 ◽  
Vol 23 (1-2) ◽  
pp. 151-165 ◽  
Author(s):  
M.F. Overton ◽  
W.A. Pratikto ◽  
J.C. Lu ◽  
J.S. Fisher
Keyword(s):  
Grain Size ◽  
Laboratory Investigation ◽  
Dune Erosion ◽  
Sand Grain Size

Grain Size Distribution Effect on Mechanical Behavior of Nanocrystalline Materials

2004 ◽  
Vol 821 ◽  
Author(s):  
A.V. Sergueeva ◽  
N.A. Mara ◽  
A.K. Mukherjee
Keyword(s):  
Grain Size ◽  
Mechanical Behavior ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Nanocrystalline Materials ◽  
Tensile Deformation ◽  
Size Structure ◽  
Niti Alloy ◽  
Distribution Effect ◽  
The Matrix

AbstractGrain size distribution effect on the mechanical behavior of NiTi and Vitroperm alloys were investigated. Yielding at significantly lower stresses than found in equiaxed counterparts, along with well defined strain hardening was observed in these nanocrystalline materials with large grains embedded in the matrix during tensile deformation at temperatures of 0.4Tm. At higher temperature the effect of grain size distribution on yield stress was not revealed while plasticity was increased in 50% in NiTi alloy with bimodal grain size structure.

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