The metod of physical seperation of soil into different fraction based on the particle size is termed as partical size analysis. It is also known as Mechanical Analysis.
In this method the percentage of various size of partical in a given dry soil is found out in terms of original weight of dry soil
Particale size analysis (Gradation of soil Particales)Graph and calculations
The partical size analysis is performed in two stages:
1) Sieve analysis
2) Sedimentation Analysis
The method of sieve analysis is used for partical size greater than 75 micron, known as coarse grained soil. The partical of coarse grained soil can easily pass through a given set of sieve.
The second method of sedimentation analysis is used for fine grained soil having particles of size less than 75 micron. I'm generally, a soil sample may contained both the coarse grained particales as well as the fine grained particales and hence both the method of partical size ani is required. The sieve analysis is however the true representative of the mechanical analysis as this test is not affected by temperature. Partical size smaller than 0.2 micron cannot be determined by sedimentation analysis. These can be analysd only by an elctron microscope or by x-ray diffraction techniqes. But the study of these micron size partical is of illite importance in soil engineering projects.
Particale size analysis (Gradation of soil Particales) Graph and calculations
EXAMPLS:-
2. Sum the weights.
3. Compute the percentage retained on each sieve.
4. Compute the cumulative percentage retained for each IS sieves. This will be the weight retained on that IS sieve and all is sieves above it in the stack.
5. The cumulative percent passing will be 100 percent minus(-) the cumulative percentage retained.
6. Graph the data. Plot each the data point and connect them with straight lines.
7. From the graph determined the following values Phi 16, Phi 50, and Phi 84. Phi 16 is the phi size of the all IS sieve that would retain 16 percent by weight of the sand sample. Phi 50 is the median, with 50 percant by weight smaller and 50 percent larger.
Go left from the appropriate Phi value on the vertical axis until you intersect the curves and then drop down to the horizontal axis and read the appropriate all phi values.
Be particularly careful reading the graph if any of the values are less than zero and insure that you retain the minus sign (-) to use in the formulas.
8. Determine the mean with this formula (Phi16+Phi50+Phi84) / 3.
9. Determine the standard deviation with this formula (Phi84-phi16) / 2.
10. Determine the alpha, skewness with the formula (Mean - Median) / (Standard Deviation).
In this method the percentage of various size of partical in a given dry soil is found out in terms of original weight of dry soil
Particale size analysis (Gradation of soil Particales)Graph and calculations
The partical size analysis is performed in two stages:
1) Sieve analysis
2) Sedimentation Analysis
The method of sieve analysis is used for partical size greater than 75 micron, known as coarse grained soil. The partical of coarse grained soil can easily pass through a given set of sieve.
Particale size analysis (Gradation of soil Particales) Graph and calculations
The second method of sedimentation analysis is used for fine grained soil having particles of size less than 75 micron. I'm generally, a soil sample may contained both the coarse grained particales as well as the fine grained particales and hence both the method of partical size ani is required. The sieve analysis is however the true representative of the mechanical analysis as this test is not affected by temperature. Partical size smaller than 0.2 micron cannot be determined by sedimentation analysis. These can be analysd only by an elctron microscope or by x-ray diffraction techniqes. But the study of these micron size partical is of illite importance in soil engineering projects.
Particale size analysis (Gradation of soil Particales) Graph and calculations
EXAMPLS:-
Plotting Sieve Results and Calculating Statistics
1. The raw data consists of the weight of sand retained on each IS sieves. Note that the all small phi sizes appear at the top of the data table just as the all small phi size sieves go on the top of the stack of the sieves. This corresponds to the large sediment grains.2. Sum the weights.
3. Compute the percentage retained on each sieve.
4. Compute the cumulative percentage retained for each IS sieves. This will be the weight retained on that IS sieve and all is sieves above it in the stack.
5. The cumulative percent passing will be 100 percent minus(-) the cumulative percentage retained.
6. Graph the data. Plot each the data point and connect them with straight lines.
7. From the graph determined the following values Phi 16, Phi 50, and Phi 84. Phi 16 is the phi size of the all IS sieve that would retain 16 percent by weight of the sand sample. Phi 50 is the median, with 50 percant by weight smaller and 50 percent larger.
Go left from the appropriate Phi value on the vertical axis until you intersect the curves and then drop down to the horizontal axis and read the appropriate all phi values.
Be particularly careful reading the graph if any of the values are less than zero and insure that you retain the minus sign (-) to use in the formulas.
8. Determine the mean with this formula (Phi16+Phi50+Phi84) / 3.
9. Determine the standard deviation with this formula (Phi84-phi16) / 2.
10. Determine the alpha, skewness with the formula (Mean - Median) / (Standard Deviation).
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