Foundation, Concrete and Earthquake Engineering

Shear Strength Parameter of Loess Soil

Dear reader we have discussed about permeability of loess soil in previous post, here we will discuss about another engineering property of loess, shear strength. We will discuss about shear strength parameter- friction angle and cohesion here.

Being spread over many parts of the world, we have to learn about behavior of loess soil and shear strength is one of the most important properties that are required in designing foundation of building.
Sinkhole wall in road pavement having loess foundation
The shear strength parameters (cohesion and internal friction angle) depend on following factors of loess:

a. Clay content in loess

b. Moisture content

c. Initial density

It was reported by sheeler, 1968 that for a soil sample having moisture content below its saturation, the internal friction angles remain in the range of 28 degree to 36 degree.

Cohesive strength of soil usually falls between (0-70) psi. The higher value indicates soil sample of higher unit weight.

Sheeler also found that when clay content in loess is increased the cohesive strength is also increased.

The findings also followed that collapse nature of loess i.e. the shear strength of dry and wet loess soil have remarkable difference. Though with moisture content all types of soils lose their strength, the loess shows much more reduction in shear strength which definitely indicates its collapse nature. Thus a dry soil sample shows better resistance to shear failure for a certain load and greater cohesion too.

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