Soil Sample

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  • Topic: Civil engineering, Particle size distribution, Geotechnical engineering
  • Pages : 2 (384 words )
  • Download(s) : 286
  • Published : November 23, 2010
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D10 = 0.078mm
D30 = 0.125mm
D60 = 0.55mm

Cc = (D30)2 / [D10 x D60]
= 0.1252 / [0.55 x 0.078]
= 0.36422 < 1

Cu = D60 / D10
= 0.55 / 0.078
=7.0513 > 6

If a soil is well-graded, it should satisfy
1 < Cc < 3
Cu > 4 (for gravels)
Cu > 6 (for sand)

Note that, from our result, Cc is much smaller than one. So by the constraints 1 < Cc < 3, we can conclude that the testing soil is not well-graded, but poorly graded. And the Cu obtained is 7.0513 > 6, which implies that the sample should be sand but not gravels. Furthermore, we may classify the sample following the table below accurately:

As we see our sample contains 17.16% of gravel which satisfy the constraints of gravelly sand. So we may further conclude that the sample is poorly-graded gravelly sand. (3) For the engineering application of results, we may see that as sieve analysis test (dry sieve) results in gradation of sample in well-graded or poorly graded on the basis of their particle sizes and its size distribution, so the result can be an indicator of other engineering properties such as compressibility, shear strength, and hydraulic conductivity which is important in construction engineering and geotechnical engineering. In an engineering design, the gradation of soil often controls the design and ground water drainage of the site. For example a poorly graded soil will have better drainage than a well graded soil because there are more void spaces in a poorly graded soil. And other example is a well graded soil is able to be compacted more than a poorly graded soil. Most types of projects may have gradation requirements that must be met before the soil to be used is accepted.

From the above result, the sample is classified as poorly-graded gravelly sand. The result is useful for the type of use of the site in further development. These poorly graded stone is good for drainage but not as a kind of foundation...
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