Effect of Relative Density on the Liquefaction Susceptibility of a Fine Sand under Controlled-Stress Loading

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.

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Liquefaction Susceptibility of Silty Sands and Low Plastic Clay Soils

International Journal of Geotechnical Earthquake Engineering ◽

10.4018/ijgee.2019070101 ◽

2019 ◽

Vol 10 (2) ◽

pp. 1-17

Author(s):

Akhila M. ◽

Rangaswamy K. ◽

Sankar N.

Keyword(s):

Axial Strain ◽

Clay Fraction ◽

Fine Sand ◽

Cyclic Stress ◽

Clay Soils ◽

Liquefaction Resistance ◽

Plastic Clay ◽

Liquefaction Susceptibility ◽

Soil Mixtures ◽

Plastic Clays

The present study evaluates the liquefaction susceptibility of non-plastic silty sands and low plastic clay soils at different cyclic stress levels under undrained triaxial loading conditions. Six different types of soil combinations were prepared after blending the silt and clay fractions into the fine sand. Silty sands contain up to 40% non-plastic fines and low plastic clays comprise 10-20% clay fraction. The cylindrical soil specimens were constituted at the medium relative density and isotropically consolidated at 100 kPa pressure. The consolidated specimens were subjected to cyclic stress amplitudes of 0.127, 0.152 and 0.178 using sinusoidal wave loading at a frequency of 1 Hz. Results were presented in terms of pore pressure build-up and axial strain propagation with load cycles, and liquefaction resistance curves. It was found that the non-plastic silty sands and soil mixtures with plasticity indices up to 15 are more susceptible to liquefaction than the fine sands. The criterion on liquefaction susceptibility of low plastic soil mixtures shows that the soil mixtures with plasticity indices up to 15 containing 20% plastic fines exhibit a sand-like behavior and show higher liquefaction susceptibility than fine sands. It is worthy to note that the low plastic soil mixtures with PI ≥ 10 are more resistant to liquefaction than the silty sands (those contain up to 40% non-plastic fines).

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Study on Permeability of Steel Slag and Steel Slag Modifying Silt Soil as New Geo-Backfill Materials

Advances in Civil Engineering ◽

10.1155/2019/5370748 ◽

2019 ◽

Vol 2019 ◽

pp. 1-14 ◽

Cited By ~ 2

Author(s):

Liyan Wang ◽

Jiatao Yan ◽

Qi Wang ◽

Binghui Wang ◽

Aimable Ishimwe

Keyword(s):

Relative Density ◽

Permeability Coefficient ◽

Steel Slag ◽

Fine Sand ◽

Particle Analysis ◽

Physical Parameters ◽

Permeability Coefficients ◽

Variable Head ◽

Backfill Materials ◽

Constant Head

To make steel slag being reasonably used in geotechnical backfilling projects or soft foundation treatment projects, three kinds of steel slag such as fine, coarse, and gravel steel slag were studied through particle analysis tests, relative density tests, and specific gravity tests to obtain basic physical parameters. Considering the influence of relative density, gradation, and other factors, constant head permeability tests of pure steel slag and variable head permeability tests of modified silt soil with different mixing contents of steel slag were carried out to test permeability coefficients under various working conditions. Prediction formulas on the permeability coefficients of the three kinds of pure steel slag and steel slag-treated silt soil were, respectively, deduced. It was concluded that the permeability coefficient of pure steel slag was greatly influenced by particle size and relative density, similar to the case of permeability coefficients of fly ash and fine sand in their dense states, and the larger the relative density was, the smaller the permeability coefficient was. The permeability coefficient of steel slag-treated silt soil increased with increasing of mixing content of steel slag, showing that steel slag can obviously improve the permeability performance of silt soil. Research results provide reference for design and construction on the application of steel slag in roadbed backfill, steel slag modifying silt soil, and other projects.

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Effect of Non-Plastic Fines on Liquefaction Resistance and Pore Pressure Behavior of Fine Sand

International Journal of Geotechnical Earthquake Engineering ◽

10.4018/jgee.2011070105 ◽

2011 ◽

Vol 2 (2) ◽

pp. 57-70

Author(s):

C. Hanumantharao ◽

G. V. Ramana

Keyword(s):

Relative Density ◽

Pore Pressure ◽

Fine Sand ◽

Standard Test ◽

Triaxial Tests ◽

Liquefaction Resistance ◽

Sand Liquefaction ◽

Test Parameter ◽

Pressure Behavior ◽

The Given

The liquefaction behavior of sand-silt mixtures is highly debatable. Various conflicting opinions are prevalent in literature, as no unique test parameter exists that can be used to express the effect of non-plastic fines on liquefaction resistance of sand. Thus, the present study critically reviews and summarizes the effect of non-plastic fines on liquefaction resistance of sand along with the test parameter and the range of fines contents used to arrive at the given conclusion. In addition, several stress controlled cyclic triaxial tests were conducted on fine Yamuna sand with varying percentages of non-plastic silt. In the current study, relative density has been adopted as the standard test parameter, as it can be directly correlated to the standard penetration value in the field. Results shows that if non-plastic fines are added to sand, liquefaction resistance increases below the limiting silt content and then liquefaction resistance decreases as further addition of fines when relative density is constant. As long as the fines are non-plastic, the pore pressure behavior is similar to that of sands and can be represented with the simple models.

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