Determination of Dry Density by Sand Replacement Method

Introduction:
A hole of specific dimensions is excavated in soil. The mass of soil excavated is calculated out.  The volume of hole is determined by filling the hole with sand of known dry density. The volume of hole is equal to the mass of sand in hole divided by its dry density. Dry density of excavated soil is calculated as

Equipment:

1. Sand pouring cylinder
2. Calibrating container of 100 mm diameter and 150 mm height
3. Soil cutting and excavation tool.
4. Glass plate of 450mm square and 9mm thickness.
5. Metal container to collect excavated soil.
6. Metal tray, 300 mm square and 40mm deep with a hole of 100 mm diameter at its center.
7. Weighing balance, moisture content cans, oven and desiccators.
8. Clean uniform sand passing from 1mm diameter sieve and retaining on 600 micron sieve.

Procedure Part -1 (Calibration)

1. Determine the internal volume of calibrating cylinder by filling it with water and mass of water required to fill. Volume may also be calculated from measuring internal dimensions of container.
2. Fill the sand pouring cylinder with sand up to 10 mm of its top. Determine mass of cylinder to nearest gram (M1).
3. Place sand pouring cylinder on calibrating container. Open the shutter and allow sand to fall in to calibrating cylinder up to the time when there is no movement of sand is noticed; then close the shutter.
4. Lift the pouring cylinder and weigh it up to nearest gram (M3)              
5.  Now again fill the cylinder up to 10mm.
6. Open the shutter and allow again the sand to run out of cylinder. When volume of sand let out equal to calibrating cylinder; close the shutter.
7. Place the cylinder over a plane glass plate .open the shutter; sand will fill the internal cone of cylinder.
8. Close the shutter when there is no movement of sand is noticed.                
9. Remove the cylinder from glass plate; collect sand; weight the sand (M2)
10. Determine dry density of sand as shown in table. 

 
Procedure part-2 (Dry Density)

1. Expose 450 mm square area on ground. Trim surface down to level earth by scrapping tool.
2. Place metal tray on leveled surface.
3. Excavate the hole in soil through central hole in the tray as a pattern. Depth of hole should be about 150 mm.
4. Collect soil and determine mass of it (M).
5. Remove metal tray from excavated hole.
6. Fill the sand pouring cylinder with sand up to 10 mm of its top. Determine mass of cylinder to nearest gram (M1).
7. Place cylinder over the hole and let the soil fall from hole by opening shutter. Close the shutter when there is no movement of sand is noticed.
8. Remove the cylinder from hole and find out its mass (M4).    
9. Take soil sample to calculate water content in soil.
10. Determine dry density of sample as explained in observation part-2.

Observation Part-1

1. Volume of calibrating cylinder=V_C
2. Mass of pouring cylinder filled with sand=M₂
3. Mass of pouring cylinder after pouring sand in to calibrating cylinder= M₃
4. Mass of sand in calibrating cone=M₂
5. Mass of sand in calibrating container Mc=M₂-M₁-M₃
6. Dry density of sand=M_c/V_c

Observation Part-2

1. Mass of excavated soil =M
2. Mass of cylinder filled with sand=M₁
3. Mass of pouring cylinder after pouring sand in hole=M₄
4. Mass of sand in hole Ms =M₁-M₄-M₂
5. Volume of sand in hole= Ms/ρ_s
6. Bulk density, ρ =M/V
7. Water content = w
8. Dry Density of Soil = ρ /(1+w)

Conclusion:

The test is precise soil testing method which gives reliable results.
This method is laborious and time consuming than core cutter method.