 # For a gravel with D 60 = 0.48 mm, D 30 = 0.25 mm, and D 10 = 0.11 mm, calculate the uniformity coefficient and the coefficient of gradation. Is it a well-graded or a poorly graded soil? ### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
Publisher: Cengage Learning
ISBN: 9781305970939 ### Principles of Geotechnical Enginee...

9th Edition
Braja M. Das + 1 other
Publisher: Cengage Learning
ISBN: 9781305970939

#### Solutions

Chapter
Section
Chapter 2, Problem 2.1P
Textbook Problem

## For a gravel with D60 = 0.48 mm, D30 = 0.25 mm, and D10 = 0.11 mm, calculate the uniformity coefficient and the coefficient of gradation. Is it a well-graded or a poorly graded soil?

Expert Solution
To determine

Calculate the uniformity coefficient, the coefficient of gradation, and state is it a well-graded or a poorly-graded soil.

The uniformity coefficient is 4.36_.

The coefficient of gradation is 1.18_.

### Explanation of Solution

Given information:

The diameter of the particle corresponding to 60% finer (D60) is 0.48mm.

The diameter of the particle corresponding to 30% finer (D30) is 0.25mm.

The diameter of the particle corresponding to 10% finer (D10) is 0.11mm.

Calculation:

Calculate the uniformity coefficient (Cu) using the relation.

Cu=D60D10

Substitute 0.48mm for D60 and 0.11mm for D10.

Cu=0.480.11=4.36

Hence, the uniformity coefficient is 4.36_.

Calculate the coefficient of gradation (Cc) using the relation.

Cc=D302D60×D10

Substitute 0.48mm for D60, 0.25mm for D30, and 0.11mm for D10.

Cc=0.2520.48×0.11=0.06250.0528=1.18

Hence, the coefficient of gradation is 1.18_.

The value of uniformity coefficient is greater than 4 (Cu>4) and the coefficient of gradation lies between 1 and 3. Hence, the type of soil is termed as well graded soil.

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