Sand Replacement Test : GNDEC

SAND REPLACEMENT

TESTSawanpreet SinghAnoop Singh

Engineering Soil Testing

Objectives

Density of soil.

Bulk density of soil. Dry density of soil. Water content. Void ratio. Degree of saturation.

Applications

Stress in soil - due to overburden pressure. Bearing capacity of soil. Settlement of footings. Earth Pressure behind retaining wall, dam,

embankments. Stability of natural slopes, dams, embankments. Field Compaction of soil. Permeability. Relative density. Void ratio, porosity, degree of saturation.

Basics Density is mass per unit volume. Density : Mass

Volume

For same volume: Cotton Steel Less mass, less density More mass,

more density

Principle

Density = Mass/Volume

For sand,

Volume : known (calibrating cylinder)Mass : known (mass of sand in calibrating

cylinder)

Density can be calculated.

Principle

Volume = Mass/Density

For Soil,

Mass : known (mass of sand in hole)Density : known (calculated earlier)

Volume of hole can be calculated.

Principle

Density = Mass/Volume

For Soil,

Mass : known (mass of excavated soil)Volume known (calculated earlier)

Density can be calculated.

Principle

Density(soil) = Mass(soil) Volume(hole)

Volume(hole) = Mass(sand) Density(sand)

Density(sand) = Mass(sand) Volume(cylinder)

Density(soil) = Mass(soil) Volume(hole)

Volume(hole) = Mass(sand) Density(sand)

Density(sand) = Mass(sand) Volume(cylinder)

Apparatus

Sand pouring cylinder Trowel or bent spoon Cylindrical calibrating container Metal tray with hole Sand – clean oven dried, passing through 600

micron sieve Weighing balance Glass plate

Sand Pouring Cylinder

Cylindrical calibrating cylinder

100 mm diameter, 150 mm height

Metal tray with hole

300 mm square,

40 mm deep,

with a hole of

100 mm diameter

in centre

Procedure

Calibration of apparatus

Measurement of soil density

Calibration

Step 1

Measure internal volume of calibrating container from volume of water required to fill the container.

Calibration

Step 2

Fill the pouring cylinder with sand within about 1cm of top and weigh it.

Step 3

Place the pouring cylinder concentrically on the top of calibrating cylinder.

Calibration

Step 4

Open the shutter to allow the sand to run out and fill the container.

Step 5

When there is no further movement of sand in the pouring cylinder, close the shutter.

Remove the cylinder and weigh it.

Calibration

Step 6

Place the pouring cylinder on a place surface such as glass plate.

Step 7

Open the shutter to allow the sand to run out.

When there is no further movement of sand in the pouring cylinder, close the shutter.


Measurement of Soil Density

Step 1

Fill the pouring cylinder with sand within about 1cm of top and weigh it.

Step 2

Clean and level the ground where the field density is required.

Measurement of Soil Density Step 3

Place the metal tray with the central hole over the portion of soil to be tested.

Step 4

Excavate the soil approximately 10 cm diameter as of hole in tray and 15 cm deep.

This volume will be approximately same as that of calibrating container.


Step 5

Collect the excavated soil in metal tray and weigh it.

Step 6

Water content of excavated soil can be determined later on by drying the excavated soil and weighing it.


Determination of Water Content :

mass of water = mass of wet soil – mass of dry soil

water content, W = mass of water X 100 mass of dry soil

Measurement of Soil Density Step 7

Place the pouring cylinder over the hole so that base of cylinder covers the hole concentrically.

Step 8

Open the shutter to allow the sand to run out into the hole.

When there is no further movement of sand, close the shutter.


Precautions

If for any reason, depth of excavation is changed, calibrating cylinder of comparative depth should be used.

Hole should not be enlarged by levering the digger against the side of the hole.

No loose material should be left in the hoe. Initial height of sand should be kept same

during calibration and measurement. There should be no vibrations during the test. Since dry density of soil varies from place to

place, repeat the test at several points and take average.

Observations and Calculations




Result