**Grading Curve **

The graphical representation of sieve analysis is also knows as Grade curve.

1. Readings recorded from sieve analysis is plotted in graph shown below (take particle size on X-axis and percent finer on Y-axis). This graph is also known as Grading Curve.

2. With respect to this graph 10%, 30% and 60% finer, and dimeter from graph is also designated as D_{10}, D_{30 }and D_{60}

3. Calculate the Coefficient of uniformity (C_{u})and Coefficient of curvature (C_{c}) by using following equations,

C_{u = }D_{60}/ D_{10}_{}

C_{c = }D^{2}_{30}/ (D_{60 }x D_{10})

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**Uniformity Coefficient (C**_{u}):

_{u}):

- · The Uniformity coefficient is express as the ratio of D
_{60}to D_{10}. - · Where D
_{60}is the value where the particle size of aggregates are 60% finer and 40% are coarser. - · And D
_{10}is the value where the particle size of aggregates are 10% finer and 90% are coarser. _{· }And Cu is calculated as, C_{u = }D_{60}/ D_{10}- · If Cu is greater than 4: Soil is classified as well graded
- · If Cu is less than 4: Soil is classified as poorly/unifromly graded

**Coefficient of Curvature (Cc):**

- · The coefficient of curvature is express of D
_{30, }D_{60}and D_{10}. - · Where D
_{30}is the value where the particle size of aggregates are 30% finer and 70% are coarser. - · D
_{60}is the value where the particle size of aggregates are 60% finer and 40% are coarser. - · And D
_{10}is the value where the particle size of aggregates are 10% finer and 90% are coarser. - · And Cc is calculated as,

- · If Cc is between 1 to 3: Soil is classified as well graded
- · If Cu and Cc is equal to 1: Soil is classified as single sized soil mass.