This is a continuation of the previous article I posted How to do a compaction test or In-situ density test, about the calculation of the compaction test report. Here we are going to compute the bulk density of sand down to the degree of compaction of soil.
I would really want to pursue this article just to completely show the full process of getting the results of the test from taking the samples into calculations. So every site engineer, project engineer, and consultant, inspector, as well as engineering students should know how it is done. This would be a guide and help them learn the procedures.
Here are the steps of calculations to determine the compaction test or In-situ density test report.
1. Compute the Bulk Density of Sand
The calculation of bulk density of sand shall be made in the laboratory before moving on to the site. Here are the values tabulated below.
|Values taken from the laboratory|
|V||0.00785 m³||Volume of calibrating container|
|M1||17,050 gm||Mass of the sand before pouring in the container|
|M2||3,425 gm||Mean value of mass of the sand in cone|
|M3||2,192 gm||Mean value of mass of the sand retained in the pouring cylinder|
Then calculate the Ms, mass of sand to fill the container. From the formula in the article linked above.
Ms = 17, 050 – 3, 420 – 2, 192
Therefore, Ms = 11, 438 gm.
Bulk density of sand, ρs = 11, 438 gm/ 0.00785 m³
Therefore, ρs = 1, 457. 07 Kgm/m³.
2. Calculate the Bulk Density of Soil
After getting all the values from the actual compaction test done on site. Let us go directly to the calculations because what we are really concerned about here is “how to get the degree of compaction?” and how it is computed? So if you have with you right now the test report from the third-party laboratory, you might try to use the solutions we’ve done here in order for you to know how the test report is computed.
Below is the parameter for the calculation of bulk density of soil which was obtained from the actual compaction test on site. From Item 5 on “How to do a compaction test or In-situ density test” the excavated soil from the hole shall place into a clean container or plastic container. It will be weighted as mass of the soil excavated (Me).
|Values taken on site|
|Me||10, 345 gm||Mass of the soil excavated|
|M1||17, 050 gm||Mass of sand before pouring into the hole|
|M2||3, 425 gm||Mass of sand in cone (mean value)|
|M4||5, 155 gm||Mass of sand after pouring into the hole (mean value)|
Mf = 17, 050 – 3, 425 – 5, 155
Therefore, Mf = 8, 470 gm
Bulk density of soil, ρso = (10, 345 gm /8, 470 gm) x 1. 45 mg/m³ = 1.78 Mg/m³
3. Calculation of Moisture Content.
Below is the laboratory test of the same sample taken from the site.
Wc = 177.5 gm. – Mass of container in gm.
W1 = 1,045.7 gm. – Mass container and moist specimen in gm.
W2 = 975.6 gm. – Mass of container and oven-dried specimen in gm.
Mass of the water
Ww = W1 – W2 = 1, 045.7 – 975.6 = 70.1 gm.
Mass of the Solid particle
Ws = W2 – Wc = 975.6 – 177.5 = 798.1 gm.
MC = (Ww/Ws) x 100 = (70.1/798.1) x 100
Therefore, MC = 8.78 %
4. Calculate the Dry Density of Soil
After getting the result of moisture content you can now calculate the ρd from the formula written in “How to do a compaction test or In-situ density test.”
ρd = (100 x 1.78)/(100 + 8.78)
Therefore, ρd = 1. 64 Mg/m³
5. Calculate the Degree of Compaction
The degree of compaction is the basis and or the final acceptance once it is passed. The specification commonly says “The degree of compaction shall be not less than 95 percent of maximum dry density (MDD).”
Please note that you have to take first a sample soil where you are going to do compaction test and test it for “Proctor test“ where you will get the maximum dry density or MDD that will use in the calculation of the Degree of Compaction.
DOC = (1.64/ 1.7) x 100
Degree of compaction, DOC = 96.5 %
The compaction test is passed and satisfactory because 96.5 percent is higher than the limit of 95 percent. The succeeding activity can now proceed.
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