Unit Weight Determination of Soil and Density Calculation

Unit weight can be determined by using core cutter method, water displacement method, sand replacement method and water balloon method.

Unit Weight Determination of Soil and Density Calculation

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Methods to determine the unit weight of soil

• Core Cutter Method
• Water displacement method
• Sand replacement method
• Water balloon method

Core Cutter Method

This method is used for cohesive soils.

• Take a core from the ground.
• Find out the weight and volume of the core.
• Calculate the bulk and dry unit weight from the corresponding formulae

Water displacement method

Archimedes principle is used. Fill the container with water and place this container in a larger tray. Drop the soil into the water filled container, some of the water may gets spilled to the outside.

• Volume of water spilled = Volume of soil sample.

To avoid the disintegration of soil when it comes into contact with the water, apply the paraffin wax coating around the soil. Then deduct this wax volume from the soil volume

Unit Weight Determination of Soil and Density Calculation

Sand replacement method

• Dig a hole in the ground
• Find the weight of the soil in the hole
• We need to calculate the volume of the hole digged
• Pore the sand into the hole to find out the volume, use cylindrical jar and other required equipments

Water balloon method

• Dig a hole in the ground.
• Place a polythene cover inside to it.
• Pore the water to find out the volume, weight can be measured and hence the unit weight

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