Foundation, Concrete and Earthquake Engineering

Strength Test for Differentiating Silt from Clay Soil

We have already discussed about importance of index properties of soil and also field identification test for differentiating one types of soil from other. Say a soil of clayey consistency can be set under unconfined compressive strength apparatus but a sandy soil is not suitable for this apparatus and should use direct shear test or other suitable apparatus for sandy soil. We will discuss about four tests for differentiating silt form clay; these are:

b. Strength test

c. Rolling test

d. Dispersion test

Of these shaking test has been discussed in our last post. We will learn about strength test here.
Sticky clay soil sample

Strength test:

The sample to be tested is prepared to for briquette; then it is left for drying. After drying, it is tested by breaking and if it broken easily, we can say it is silt. When the sample is of clay soil, it takes some effort to break this.

Another observation can be made, if the loose material of surface of briquette can be dusted off, it is silt.

While a clay sample cannot be easily dusted off.

Moreover moist clay soil provides flowing identification appearance:

a. When pressed within finger, it produce a soapy feel

b. It shows sticky feeling

c. It dries slowly

In our upcoming test we will discuss about dispersion test and rolling test used to differentiate these soils. Please stay with us.

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