How do you carry out the determination of Specific Gravity of Soil by Pycnometer Method?
The Pycnometer is chiefly utilized for the determination of the specific gravity of soil particles of both types; grained and coarse grained soils. The specific gravity of soil is computed with the utilization of following relation:
Where M1=mass of empty Pycnometer,
M2= mass of the Pycnometer with dry soil
M3= mass of the Pycnometer and soil and water,
M4 = mass of Pycnometer filled with just water
G= Specific gravity of soils
Tool and equipment for Pycnometer Test:
- Vacuum pump
- Glass rod
- Pycnometer of roughly 1 ltr capacity
- Weighing balance, which has the precision of 1g
Process for Specific Gravity of Soil by Pycnometer:
1. First of all, thoroughly clean the Pycnometer and let it for drying. Tightly fasten the cap. Measure its mass (M) to the closest of 0.1 g.
2. Mark down the cap and Pycnometer with a perpendicular line which is parallel to the axis of the Pycnometer to make certain that the cap is fastened to the similar mark every time.
3. Remove the cap and put approximately 200 g of oven dried soil inside the Pycnometer. Fasten the cap. Compute the mass (M2).
4. Unbolt the cap and augment adequate quantity of de-aired water to the Pycnometer so as to shelter the soil. Fasten on the cap.
5. Mildly shake the contents. Join the Pycnometer to a vacuum pump to eliminate the ensnared air, for approximately 20 minutes for fine-grained soils and approximately 10 minutes for coarse-grained soils.
6. Detach the vacuum pump. Fill up the Pycnometer with water, around three-fourths full. Once again apply the vacuity for around 5 minutes until the bubbles cease to appear on the surface of the water.
7. Fill up the Pycnometer with water entirely up to the marked down point. Leave it to dry it from exterior. Measure its mass (M3).
8. Note down the temperature of contents.
9. Vacate the Pycnometer. Clean it and wipe it thoroughly dry.
10. Fill up the Pycnometer with just water. Bolt on the cap up to the mark. Wipe it completely dry. Measure its mass (M4).
Table: Observations and calculations for Specific Gravity of Soil:
| Sl. No. | Observations an Calculations | Determination No. | ||
| 1 | 2 | 3 | ||
| Observation | ||||
| 1 | Pycnometer No. | |||
| 2 | Room Temperature | |||
| 3 | Mass of empty Pycnometer (M1) | |||
| 4 | Mass of Pycnometer and dry soil (M2) | |||
| 5 | Mass of Pycnometer, soil and water (M3) | |||
| 6 | Mass of Pycnometer and water (M4) | |||
| Calculations | ||||
| 7 | M2 – M1 | |||
| 8 | M3 – M4 | |||
| 9 | Calculate G using formula | |||
Results of Pycnometer Test:
Specific gravity of soil at ___0C = _____.