The standard penetration resistance N of a granular deposit is found to be 20. The soil can be classified approximately in terms of phi and density index respectively as?

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Answer

Standard Penetration Resistance and Soil Classification

Standard Penetration Resistance (N) is a measure of the resistance of soil to penetration by a standardized sampler. The soil classification depends on the value of N and other factors such as phi and density index.

Phi Classification

The phi value is the angle of friction between the particles of soil.

If the phi value is less than 14 degrees, the soil is classified as very loose.

If the phi value is between 14 and 24 degrees, the soil is classified as loose.

If the phi value is between 24 and 34 degrees, the soil is classified as medium dense.

If the phi value is between 34 and 44 degrees, the soil is classified as dense.

If the phi value is greater than 44 degrees, the soil is classified as very dense.

Density Index Classification

Density index (ID) is a measure of the relative density of soil.

If the density index is less than 0.35, the soil is classified as loose.

If the density index is between 0.35 and 0.50, the soil is classified as medium dense.

If the density index is between 0.50 and 0.65, the soil is classified as dense.

If the density index is greater than 0.65, the soil is classified as very dense.

Soil Classification for N=20

For N=20, the soil can be classified as:

Loose or medium dense if the phi value is between 14 and 34 degrees and the density index is less than 0.50.

Dense or very dense if the phi value is between 24 and 44 degrees and the density index is greater than or equal to 0.50.

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