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TO DETERMINE IN-SITU DRY DENSITY BY SAND REPLACEMENT METHOD

Theory:

A hole of specified dimensions is excavated in the ground. The mass of the excavated soil is determined.

The volume of the hole is determined by filling it with clean, uniform sand whose dry density () is determined separately by calibration. The volume of the hole is equal to the mass of the sand filled in the hole divided by its dry density.

The dry density of the excavated soil is determined as

Where M= mass of the excavated soil, V= volume of the hole and w= water content.

Equipment:

1. Sand – pouring cylinder

2. Calibrating container, 100mm diameter and 150mm height

3. Soil cutting and excavating tools, such as scrapper tool, bent spoon

4. Glass plate, 450mm square, 9mm thick

5. Metal container to collect excavated soil

6. Metal tray, 300mm square and 40mm deep with a hole of 100mm in diameter at the centre

7. Weighing balance

8. Moisture content cans

9. Oven

10. Desiccator

Clean, uniform sand passing 1mm IS sieve and retained on 600micron IS sieve in sufficient quantity.

Part-I: Calibration

Procedure:

1. Determine the internal volume of the calibrating container by filling it with water and determining the mass of water required. The mass of water in grams is approximately equal to the volume in mililitres. The volume may also be determined from the measured dimensions of the container.

2. Fill the sand-pouring cylinder with sand, within about 10mm of its top. Determine the mass of the cylinder (M1) to the nearest gram.

3. Place the sand-pouring cylinder vertically on the calibrating container. Open the shutter to allow the sand run out from the cylinder. When there is no further movement of the sand in the cylinder, close the shutter.

4. Lift the pouring cylinder from the calibrating container and weigh it to the nearest gram (M3).

5. Again fill the pouring cylinder with sand, within 10mm of its top.

6. Open the shutter and allow the sand to run out of the cylinder. When the volume of the sand let out is equal to the volume of the calibrating container, close the shutter.

7. Place the cylinder over a plane surface, such as a glass plate. Open the shutter. The sand fills the cone of the cylinder. Close the shutter when no further movement of sand takes place.

8. Remove the cylinder. Collect the sand left on the glass plate. Determine the mass of sand (M2) that had filled the cone by weighing the collected sand.

9. Determine the dry density of sand, as shown in the data sheet, part-I.

Part-II: Dry density

Procedure:

1. Expose an area of about 450mm square on the surface of the soil mass. Trim the surface down to a level surface using a scrapper tool.

2. Place the metal tray on the leveled surface.

3. Excavate the soil though the central hole of the tray, using the hole in the tray as a pattern. The depth of the excavated hole should be about 150mm.

4. Collect all the excavated soil in a metal container, and determine the mass of the soil (M).

5. Remove the metal tray from the excavated hole.

6. Fill the sand pouring cylinder within 10mm of its top. Determine its mass (M1).

7. Place the cylinder directly over the excavated hole. Allow the sand to run out the cylinder by opening the shutter. Close the shutter when the hole is completely filled and no further movement of sand is observed.

8. Remove the cylinder from the filled hole. Determine the mass of the cylinder (M4).

9. Take a representative sample of the excavated soil. Determine its water content.

Determine the dry density of soil as shown in the data sheet, Part-II.

Data Sheet for Sand Replacement Method

Part-I: Calibration for Dry Density of Sand

 Sl. No. Observations an Calculations Determination No. 1 2 3 Observation 1 Volume of calibrating cone VC 2 Mass of pouring cylinder (M1), filled with sand 3 Mass of pouring cylinder after pouring sand into the calibrating container and cone (M3) 4 Mass of sand in the cone (M3) Calculations 5 Mass of sand in the calibrating containerMC=(2) – (3) – (4) 6 Dry density of sand=MC/VC

Part-II: Dry Density of Soil

 Sl. No. Observations an Calculations Determination No. 1 2 3 Observation 1 Mass of excavated soil (M) 2 Mass of pouring cylinder (M1), filled with sand 3 Mass of pouring cylinder after pouring into the hole and cone (M4) Calculations 4 Mass of sand in the holeMS=M1 – M4– M2 5 Volume of sand in the holeV=Ms/ 6 Bulk density =M/V 7 Water content 8 Dry density using formula

Result:

Dry density=_______g/ml.