Have you ever been asked by your consultant or your manager this question “Do you know how to do compaction test?” and “Do you know how to compute compaction test results?
A quality engineer or a civil engineer should know how the results are derived. I will first want to show you the procedure on how to conduct compaction or field density tests on site. By the way, the consultant representative or the quality engineer shall select the area to be tested and shall mark it on the drawing.
There are many ways to determine the compaction of soil but here I used Sand Replacement Method, which we are using on our site. And before blinding works, you have to make sure that the inspection request is submitted to the consultant and the compaction test report is passed.
But first, here are the apparatus and equipment for the In-situ density test.
| Apparatus for In-Situ Density Test | |
|---|---|
| 1. Pouring cylinder | 7. Meter |
| 2. Pointed steel rod | 8. Hammer |
| 3. Large screw driver | 9. Bent spoon dibber |
| 4. Sand or silica container | 10. Gloves |
| 5. Glass plate | 11. Metal trays, 500mm square, 50mm depth with 200mm dia. hole in the center |
| 6. Sample container (plastic bag or plastic container) | |
Here is the procedure on how to do the Compaction test or In-Situ Density test.
1. Place the metal tray
The technician can now place the metal tray as per the Consultant or Quality Engineer’s preferred location. As a Quality Engineer, you should make sure that the area to be tested is compacted and within the area submitted in the Inspection Request.
2. Marking the sample container
As QC Engineer, you should see to it that the sample container is marked by a technician of its location and other related markings, just make sure all the marks are correct.
3. Digging the soil
A helper will start to dig the soil by a using pointed steel rod (250mm long 16 – 20 mm dia.) and a hammer. The head of the rod shall be stricken at slow speed and at conditional pressure. Use gloves for hand protection to prevent hand injury.
4. Putting the loose soil in the sample container
The dug loose soil shall be placed in the sample container, make sure there are no any pieces of soil shall be wasted otherwise, it will affect the results of compaction.
5. Measuring the depth of the hole
While the digging progresses, monitor the depth of the hole by measuring a ruler, make sure that the depth is 200 mm or 150 mm depending on the requirement of the specification. If the depth is not yet achieved continue digging until it reaches the desired or required depth.
6. Pouring silica in the hole
Once the hole is properly shaped to the diameter of 200 mm just the same diameter that of the hole of the metal tray and the depth has reached. Place the pouring cylinder onto the metal tray. Pour the silica inside the pouring cylinder, make sure no one will hold or touch the pouring cylinder that may cause vibration.
7. Taking the silica from the hole
The hole, once filled with silica and when the hole has fully filled, remove the silica and place it to an extra container it may use again for the next set of compaction.
Here are now the formulas to compute the compaction test or In-situ density test.
Det. the bulk density of Sand.
ρₛ = mₛ / V
Where,
mₛ = m₁ – m₂ – m₃
| Formula for Bulk Density of Sand | |
|---|---|
| ρs | Bulk density of sand (Mg/m³) |
| Ms | Mass of sand to fill the container (in gm.) |
| V | Vol. of container (in mL) |
| M1 | Mass of sand before pouring in the container (in mg.) |
| M2 | Mass of sand in cone (in gm.) |
| M3 | Mass of sand after pouring the container (in gm.) |
Det. the bulk density of soil.
ρₛₒ = (mₑ / m) x ρₛ
where,
m = m₁ – m₂ – m₄
| Bulk Density of Soil | |
|---|---|
| ρso | Bulk density of soil (Mg/m³) |
| Me | Mass of soil excavated (in gm.) |
| Mf | Mass of sand required to fill the hole (in gm.) |
| M1 | Mass of sand before pouring into the hole (in gm.) |
| M2 | Mass of sand in cone (in gm.) |
| M4 | Mass of sand after pouring into the hole (in gm.) |
Det. the dry density.
ρⅆ = (100 x ρₛₒ) / ( 100 + ω)
Det. the degree of compaction.
DOC = ( ρⅆ / MDD) x 100
Related Article: How To Calculate A Compaction Test Report
Hoping that the above has helped the Quality Engineers or Civil Engineers to better understand how the compaction test or In-situ density test using the sand replacement method is done.
Did you follow the above compaction test computation? Please write a comment if you do.
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