Question
Download Solution PDFA soil sample is subjected to laboratory sieve analysis using a complete set of standard IS sieves. Out of 3 kg of soil used in the test, 1200 gm was retained on IS 600 micron sieve, 1500 gm was retained on IS 500 micron sieve and the remaining 300 gm was retained on IS 425 micron sieve. The uniformity co-efficient for the soil is:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
Coefficient of uniformity Cu:
- It is defined as the ratio of D60 to D10.
- When Cu ≈ 1 uniformly graded soil.
- When Cu>4 well-graded gravel
- When Cu>6 well-graded sand.
Calculation:
Here, D60 = 60% particles are finer than this size, D10 = 10% particles are finer than this size.
|
Sr NO. |
Size of sieve |
Weight of soil retained (g) |
% retained |
Cumulative % retained |
% finer = 100 – (% cumulative retained) |
|
1 |
600μ |
1200 |
\(\frac{{1200}}{{3000}} \times 100 = 40\% \) |
40% |
60% |
|
2 |
500μ |
1500 |
\(\frac{{1500}}{{3000}} \times 100 = 50\% \) |
90% |
10% |
|
3 |
425μ |
300 |
\(\frac{{300}}{{3000}} \times 100 = 10\% \) |
100% |
0% |
∴ From table, D60 = 600μ and D10 = 500μ
\(\therefore {C_u} = \frac{{{D_{60}}}}{{{D_{10}}}} = \frac{{600}}{{500}} = 1.2\)
Based on the value of Cu, soil can be classified as uniformly graded soil.
Note:
1. Like Cu, there is one more shape factor called coefficient of curvature (CC) which is given by
\({C_c} = \frac{{{D_{30}}^2}}{{{D_{60}}{D_{10}}}}\).
2. Range of Cc for well graded soil is 1 ≤ CC ≤3 .
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