Foundation, Concrete and Earthquake Engineering

How does Density of Loess Soil Indicates Collapse Potential?

Dear reader in previous post we have discussed about a method for determining collapse potential of loess soil. Here we will learn about usual density of loess soil and its application in calculating collapse potential with the help of liquid limit. We are providing range of dry density and liquid limits of loess soil below:

In-situ dry density: (10-16.5) KN/m3

Liquid limit: (25-55) percent

Density of loess soil including other collapsible soil is an important (not only one but one of the most) parameters that can be used to determine collapse potential.
In 1961 Hilf and Holtz recommended that dry density together with liquid limit can be used to determine collapse potential of loess soil. 

Bowels produced a linear equation for convenience of use. This equation is 

linear equation for dry density for determining collapse potential
WL=liquid limit expressed as percent
γdry=dry density as a function of liquid limit WL and expressed as KN/m3
Examining density of loess soil
Now how to use this equation?

If in situ density of soil is found to be less than the result found from equation (1)dry), this soil is considered to have susceptibility to collapse. With increase in difference between two densities (one from equation (1) and another from in-situ value), the severity of collapse is also increased.

Though not relevant, we are including optimum moisture content and maximum dry densities of typical loess soil as this post is related to density of loess soil.

Standard compaction (ASTM D698) test, γdry= (15.5-17.5) KN/m3

Optimum moisture content= (12-20) percent.

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