Arching effect in fine sand due to base yielding

2010 ◽  
Vol 47 (3) ◽  
pp. 366-374 ◽  
Author(s):  
Jamshid Sadrekarimi ◽  
Alireza Abbasnejad
Keyword(s):  
Relative Density ◽  
Experimental Work ◽  
Fine Sand ◽  
Soil Mass ◽  
Flow Process ◽  
Flow Phenomenon ◽  
Dense Sand ◽  
Arching Effect ◽  
Different Diameters ◽  
Upper Boundary

This paper presents results of an experimental work on the arching effect in loose and dense sand. The apparatus comprises concentric circular trapdoors with different diameters that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole mass of soil deforms elastically. However, after a specified displacement that depends on the trapdoor diameter and soil relative density, the soil mass behaves plastically. This behavior, which is due to flow phenomenon, continues until the stress applied onto the trapdoor decreases to a minimum value. Then the stress carried by the trapdoor shows an ascending trend. This indicates the gradual separation of the yielding mass from the whole soil body. Finally, the flow process creates a stable arch of sand. This process is called the arching mechanism. Depending on the trapdoor diameter, there is a critical relative density at and beyond which the test leads to the formation of a stable arch. The results are also compared with Terzaghi’s theory and the assumption of an upper boundary solution is discussed.

Soil Stresses on Carbon Steel Pipe Undergoing Uplift

2016 ◽  
Vol 835 ◽  
pp. 439-443
Author(s):  
Yuri D. Costa ◽  
Lucas S. Moraes ◽  
Carina L. Costa
Keyword(s):  
Carbon Steel ◽  
Relative Density ◽  
Numerical Study ◽  
Three Dimensional ◽  
Soil Mass ◽  
Steel Pipe ◽  
Surcharge Loading ◽  
Flexible Pipes ◽  
Stress Variations

This paper presents a three-dimensional numerical study to evaluate the variations in stresses in the soil mass surrounding a carbon steel pipe class API 5L X60 submitted to uplift due to ground elevation. Analyses were carried out for soil relative density, pipe stiffness and surficial surcharge loading. Results have shown that stress variations due to uplift are lower for looser backfill soils and flexible pipes. Stress variations in pipe invert are meaningful in the vicinity of the region between stable and unstable soil masses.

Study on Load-Bearing Mechanism of Stabilizing Pile-Groups by FEM and its Application

2014 ◽  
Vol 638-640 ◽  
pp. 656-670
Author(s):  
Huan Feng Qiu ◽  
Shao Jun Fu
Keyword(s):  
Computer Code ◽  
Soil Mass ◽  
Design Parameters ◽  
Pile Groups ◽  
Soil Pressure ◽  
Soil Arching ◽  
Fine Grained ◽  
Arching Effect ◽  
Soil Arching Effect ◽  
Pile Diameter

The behaviour of pile-groups subjected to lateral soil pressure is a key consideration in establishing the design parameters of pile-groups. In this paper, one representative section of the Chongqing Jiangdong slope is taken as an example. The existence of an arching zone around pile groups for granular and fine-grained soils is first examined using the finite element computer code CORE-3D. Pile load-displacement curves and the arching effect are considered together to explain how the stresses are transferred from the soil to the piles. The key parameters controlling the soil arching effect are centre-to-centre pile spacing (S), thickness of stable soil mass (H), depth (L) of pile embedment, pile diameter (D) and these were studied extensively. An empirical equation summarising the results is presented and the results have been adopted by the designer in practice.

scholarly journals Response of Skirted Foundations Resting on Dry Medium Dense Sand

2018 ◽  
Vol 4 (6) ◽  
pp. 1193 ◽  
Author(s):  
Lujain Haider ◽  
Haider M. Mekkiyah
Keyword(s):  
Cross Section ◽  
Carrying Capacity ◽  
Considerable Increase ◽  
Experimental Tests ◽  
Load Carrying Capacity ◽  
Dense Sand ◽  
Load Carrying ◽  
Different Diameters ◽  
Large Soil ◽  
Settlement Behaviour

Experimental model tests were carried out to study the response of skirted foundation resting on dry sand.  The experiments were performed in a large soil container (1000  1000 mm in cross section and 800 mm in height).  Skirts with three different lengths (L) varied from 0.5D to 1.5D was attached to the edge of shallow circular foundations having three different diameters (D=60, 90 and 120 mm). Different parameters have been studied; these parameters involve skirt length, foundation size and skirt conditions. Skirts with open end and closed end were used. The relative density was kept constant and equals to 60%. The case of foundation without skirt (L=0) was initially tested and set as a reference for comparison purpose. From the results of experimental tests, it was found that the skirt modifies the load-settlement behaviour, increasing the load carrying capacity and reducing the foundation settlement. The results also indicate that load carrying capacity of skirted foundation increases with increase skirt length as well as foundation size. The results show that using skirt with closed end brought a considerable increase in load carrying capacity than that of open end.

Redescription, paleogeography, and experimental paleoecology of the Silurian phyllocarid Gonatocaris

2020 ◽  
Vol 94 (5) ◽  
pp. 906-921
Author(s):  
Joseph H. Collette ◽  
Roy E. Plotnick
Keyword(s):  
New York ◽  
Shallow Water ◽  
South China ◽  
Experimental Work ◽  
Fine Sand ◽  
Acute Angle ◽  
Grain Sizes ◽  
The Past ◽  
Work Done ◽  
Original Type

AbstractGonatocaris decora (Clarke, 1901) is an unusual, highly ornamented Silurian phyllocarid from the Pittsford Shale Member of the Vernon Formation, Salina Group of New York, that has been allied with Emmelezoe in the past due to the possession of an ‘optic tubercle.’ The systematic positions of Gonatocaris and Emmelezoe have been difficult to assess due to the lack of complete remains, attributions based on spurious characters, and missing and unfigured specimens. Relatively recent collections of Gonatocaris decora, along with a relocation of the original type material of Emmelezoe, have allowed a reexamination of all relevant genera and a more robust systematic placement for G. decora. Characters of generic importance for Gonatocaris include a greatly elongated abdomen; an acute angle of the ventral carapace margin separating distinct anteroventral and posteroventral margins from each other; and distinctive, multiscale horizontal ridge-like ornament of the carapace valves. Growth was found to be isometric. Experimental work done using a model of the scale-like ornament and multiple grain sizes of substrate indicates that cuticle ornament may have served to increase friction between the animal and a fine sand substrate, although resistance to predation is the currently favored hypothesis. Because Gonatocaris species are currently known only from the eastern margin of Laurentia and northern South China, it is likely that this genus was nektonic. Accumulations of similarly sized carapaces and other disarticulated sclerites in shallow-water settings may indicate spawning events following molting en masse.

Studying The Settlement of Backfill Sandy Soil Behind Retaining Wall Under Dynamic Loads

2020 ◽  
Vol 38 (7A) ◽  
pp. 992-1000
Author(s):  
Reham E. Hamdi ◽  
Mohammed Y. Fattah ◽  
Mohammed F. Aswad
Keyword(s):  
Relative Density ◽  
Sandy Soil ◽  
Limit Equilibrium ◽  
Retaining Wall ◽  
Retaining Walls ◽  
Dynamic Loads ◽  
Dense Sand ◽  
Burden Test ◽  
Long Time ◽  
Cohesion Less Soil

For a long time, the seismic examination of retaining walls has been contemplated by a few strategies dependent on the basic augmentation of Coulomb's limit equilibrium investigation. These techniques cannot gauge the removal of the refill soil upheld by the wall. A trial examination is completed to contemplate the vertical settlement on sandy soil under dynamic loads with other burden amplitudes, vibration frequencies, relative density, and various separations between the establishment and holding divider. The model balance utilized in this investigation is square. Dynamic burden test is done on cohesion less soil with three burden amplitudes (0.25 ton, 0.5 ton and 1 ton), three vibration recurrence (0.5 Hz, 1 Hz and 2 Hz), two density of sandy soil (30% loose sand and 70% dense sand) and three unique separations between the establishment and retaining wall. It has been seen that the change is increment with the burden of abundance and decreased by increasing the separation between the establishment and retaining wall. There is an unimportant result of recurrence on the aggregate settlement. The settlement decrement by incrementing the relative density

scholarly journals Investigation of the Transfer of Septum Microbial Contamination by Hypodermic Needles

2020 ◽  
Author(s):  
Tim Eaton ◽  
L Ramscar ◽  
J Cox ◽  
WILLIAM Whyte
Keyword(s):  
Key Words ◽  
Experimental Work ◽  
Microbial Growth ◽  
Microbial Contamination ◽  
Growth Media ◽  
Hypodermic Syringe ◽  
Syringe Needle ◽  
Different Diameters ◽  
Needle Diameter ◽  
Microbial Growth Media

The likelihood of the transfer of microbial contamination from the surface of a vial septum into the vial liquid, by penetration of a hypodermic syringe needle, has been investigated. Experimental work was carried out with vials containing sterile microbial growth media and the use of needles of three different diameters. Three different concentrations of microbes on the surface of the vial septum (10, 100, and 1000) were used. Microbial contamination that was transferred into the growth media was determined by incubation of the vials following penetration of the septum by the needles. Contamination was detected in 87% of all the vials tested, and was generally found to increase as the concentration of septum challenge organisms and needle diameter increased. Key words: Septum seals, hypodermic needles, multi-use vials, microbial contamination

scholarly journals Effect of relative density of 2D granular materials on the arching effect through numerical trapdoor tests

2022 ◽  
Vol 141 ◽  
pp. 104553
Author(s):  
Qi-Wei Liu ◽  
Han-Lin Wang ◽  
Ren-Peng Chen ◽  
Zhen-Yu Yin ◽  
Xing-Tao Lin ◽  
...  
Keyword(s):  
Relative Density ◽  
Granular Materials ◽  
Arching Effect

scholarly journals Undrained Cyclic Response and Resistance of Saturated Calcareous Sand considering Initial Static Shear Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Baojian Li ◽  
Panpan Guo ◽  
Gaoyun Zhou ◽  
Zhe Wang ◽  
Gang Lei ◽  
...  
Keyword(s):  
Shear Stress ◽  
Relative Density ◽  
Shear Stresses ◽  
Loose Sand ◽  
Calcareous Sand ◽  
Cyclic Shear ◽  
Cyclic Response ◽  
Dense Sand ◽  
Cyclic Resistance ◽  
Static Shear

Sand elements in the natural or manmade field have often undergone initial static shear stresses before suffering cyclic loading. To explore the effect of static shear stress, a series of undrained cyclic triaxial tests were performed on dense and loose calcareous sand under different initial and cyclic shear stresses. The triaxial test results are used to describe the effect of static shear stress on the cyclic response of the calcareous sand with different relative density. Cyclic mobility, flow deformation, and residual deformation accumulation are the three main failure modes under varying static and cyclic shear stress levels. The cyclic resistance of dense sand is greater than that of loose sand, but the initial static stress has different effects on the cyclic resistance of the two kinds of sand. The dense sand owns a higher cyclic resistance with SSR increasing, while for the loose sand, 0.12 is the critical SSR corresponding to the lowest value of the cyclic resistance. The dense sand has more fast accumulation of dissipated energy, compared with loose sand. Additionally, an exponential relationship is established between static shear stress, relative density, and normalized energy density.

Monitoring of micromorphological changes in a virgin Solonetz under regional changes in hydrology and climate (Northern Caspian Lowland, Russia)

2018 ◽  
Vol 8 ◽  
Author(s):  
Marina Lebedeva ◽  
Maria Konyushkova ◽  
Sergey Khokhlov
Keyword(s):  
Water Table ◽  
Soil Mass ◽  
Published Data ◽  
Research Station ◽  
Silty Clay ◽  
Clear Trend ◽  
Thin Sections ◽  
Caspian Lowland ◽  
Humus Accumulation ◽  
Upper Boundary

Over the past 40 years, a clear trend towards an increasing humidity and a rising groundwater table has been observed in the south-eastern semidesert part of European Russia. According to the published data, two clear periods of climate are distinguished: 1950s-1970s and 1970s-2000s. The thin sections of a Solonetz sampled in different periods of time (1950s, 1960s, 1970s, 1982, 2002 and 2013) at the Dzhanybek research station were studied micromorphologically to observe how these natural changes influenced soil pedofeatures. A comparison of thin sections showed no significant changes in soil properties between 1950s and 1982, when the hydrological (ground water table) and climatic parameters remained relatively stable. However, between 1982 and 2013, due to a significant increase in climatic moisture and rising groundwater, the following changes in soil microfeatures took place: the activation of humus accumulation and biogenic structuring, the eluviation of the silty clay-humus matter, the development of solodic features, gleyization of the soil mass, and the accumulation of opaque black organic grains about 2-3 µm formed in the topsoil due to the long stagnation during the springtime after snow melting. The water table rise leads to the consequent rise of the upper boundary of the accumulation of gypsum and carbonates.

Sign in / Sign up

Export Citation Format

Share Document