Determination of unit weight
The various methods used for unit weight determination are:
1. Core Cutter Method
2. Water Displacement Method
1. Core Cutter Method
2. Water Displacement Method
3. Sand Replacement Method
4. Water Balloon Method
5. Radiation Method
1. Core Cutter Method:
- It is a field test.
- It can be used only for soft fine-grained soil (cohesive soil), not for dry, gravely, or stony soil.
- It can be used when the surface of the soil is exposed and the core-cutter can be driven.
- The volume of Core= 1000cc
W1= wt. of empty core cutter.
W2= wt. of core cutter + soil.
V= Vol. of Soil known in advance.
2. Water Displacement Method:
If V1 is the volume of water displaced when total wt. W2 is immersed in the container filled with water.
Volm. of soil(V) = V1- Vwax
- It is a Lab method.
- It is used when a chunk of soil is brought from the field.
- It is used for cohesive soil.
3. Sand Replacement Method:
- This is a Field method.
- A small area is excavated, and the excavated soil sample is precisely weighed.
- A calibrated cylinder containing sand is placed over the excavated area and the pit is filled with sand.
- The volume of the pit is obtained from the calibrated cylinder.
- The bulk unit weight is calculated.
- A representative sample is tested for water content.
- It is suitable for gravelly, sandy, and dry soil in which the core cutter could not be used.
Volm of soil(V)= (Volm of sand in pit+ Volm of the conical hopper)- Volm of the conical hopper.
4. Water Balloon Method:
- In this method volume of the excavated pit is obtained by covering the pit with a thin plastic membrane and noting down the volume of the water used for filling it.
5. Radiation Method:
- Nuclear density meters are used.
- It is a quick and non-destructive method.