Foundation, Concrete and Earthquake Engineering

Index Properties of Loess Soil

Dear reader we have already learnt about grain size and shape of loess soil. Loess is a collapsible soil. Most of collapsible soils including loess are free from pebbles and gravel. Grain size distribution of loess soils is characterized by a range of (0.01-0.10) mm; though there may have some contamination. The contamination as discussed in previous posts is clay. There have also some sand particles and some contamination by organic leachates.

  • The sand particles are usually of less than 0.05 mm. Most of the particles generally pass through no.200 sieve i.e. 0.075mm. 
  • The specific gravity of loess soil remains in the range of (2.60-2.80).
  • In situ dry densities are observed to be within (10-16.5) KN/m3.
A close view of loess soil
Dear reader we know Atterberg limits of soil is an important parameter depending on which together with other parameter like standard penetration number, we can predict some engineering properties of soil. With these we have a rough idea about engineering properties and in small or unimportant foundation construction work sometimes we depend on prediction.

So we should have idea about atterberg limits of loess. Atterberg limits also known as consistency limits. Consistency limits depend mainly on clay and organic contaminants, if there have any, and the liquid limit falls within (25-55) and plastic limit lies between (15-30) percent.

The in situ porosity of loess is very high and very often it is found greater than 50 percent i.e. a void ratio of greater than 1.0 which leads to higher possibility to collapse when get saturated. The usual value of in-situ void ratio lies between (0.67-1.50).

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