The test conducted at the field to check the density of soil to ensure whether it has been compacted well as
They are otherwise known as Field Density Test or FDD Test of sand.
Density / Unit Weight – The unit weight of the material is defined as Mass per Volume (M/V)
The bearing capacity of a soil depends on the density of soil. The structural design was also calculated based on this. So to achieve the required soil density, we tend to compact and consolidate it well.
Once the compaction has been done, the sand replacement test (Cone test) will be used to determine the density of cohesionless soil.
The core test method is not possible to find the density of cohesionless soil. So the sand replacement test is used to determine the density of the soil as per the Indian Standard Code IS 2720 Part 28.
The sand replacement method is suitable for where the compacted soil layer does not exceed 150mm.
Precaution of Field Density Test
The sand is required as given below, to conduct the calibration for the apparatus.
Calibration of Apparatus
First, we have to find the bulk weight of sand to determine the bulk unit weight of soil.
V = (𝝿 hd2)/4 or (πr2h)
D = 10cm h = 12.74cm
V = 3.14 x 12.74 x 102/4) = 1000 cm3
Volume of Calibrating container V = 1000 cm3
Wc = W1 – W2 – W3
Bulk density of Sand 𐊄s = Wc / Volume of Calibrating container
𐊄s = Wc / V
DESCRIPTION |
FORMULA/NOTATION |
SAMPLE1 |
SAMPLE2 |
SAMPLE3 |
Wt of Sand pouring cylinder with sand |
W1 |
|||
Wt of the pouring cylinder which consists of remaining sand after sand-filled over the calibrating container |
W2 |
|||
Wt of Conical shape sand |
W3 |
|||
Wt of sand to fill the calibrating container |
Wc = W1 – W2 – W3 |
|||
Wt of empty calibrating container |
V = (𝝿 x h x d2)/4 |
|||
Bulk Density of Sand |
𐊄s = Wc / V |
We just finished the calibration part.
Test Procedure
Wp = W1 – W2 – W3
The volume of the sand-filled to the hole Vh = Wp/𐊄s
Now the bulk density of soil 𐊄b = We / Vh
Now the dry bulk density of soil 𐊄d = (𐊄b/1 + m)
DESCRIPTION |
FORMULA / NOTATION |
SAMPLE 1 (gram/cu. cm) |
SAMPLE 2 (gram/cu. cm) |
SAMPLE 3 (gram/cu. cm) |
Wt of excavated soil |
We |
|||
Wt of Sand pouring cylinder with sand |
W1 |
|||
Wt of the pouring cylinder which consists of remaining sand after sand-filled over the calibrating container |
W2 |
|||
Wt of Conical shape sand |
W3 |
|||
Wt of sand to fill the excavated hole |
Wp = W1 – W2 – W3 |
|||
The volume of the sand-filled to the hole |
Vh = Wp/𐊄s |
|||
Bulk Density of Soil |
𐊄b = We/Vh |
|||
Moisture content |
m |
|||
Bulk density of soil |
𐊄d = (𐊄b/1 + m) |
Happy Learning 🙂
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