The determination of dry density by the core cutter method generally involves the hammering or jacking of a steel cylinder ( with known mass and volume) into the soil thereby and determining the mass of the soil.
Core cutter method for dry density determination is commonly used for control of earthworks as well as the subgrade materials. This method is not desirable for coarse-grained soil or coarse-grained pavement materials.
Suitability of Core Cutter Method
This method of dry density determination is most desirable for the cohesive soil.
It is only used on fine-grained cohesive soils that do not contain stones.
Objectives of Core Cutter Method
The primary objective of the core cutter method is to determine the dry density of soil. It is used as a control test to check if the soil has acquired the designated dry density or not.
The determined in situ dry density is necessary for the design of pavement and highway.
1. A steel rammer of mass 9kg and the overall length including the foot and staff of about 900mm.
2. A cylindrical core cutter with 100mm internal diameter and 130mm long.
3. Weighing balance with an accuracy of 1 gram.
4. Steel dolly with 100mm internal diameter and 25mm high.
5. Palette knife.
6. Straight edge, ruler of steel etc.
The procedure for the dry density determination by the core cutter method involves the following series of steps:
i. The experimental setup of the cylindrical core cutter along with the dolly is first made.
ii. The steel dolly is then placed over the cutter to prevent the damage to the edges of the core cutter.
iii. The cylinder is then embedded into the ground up to its full height with the help of rammer and is taken out by excavating its sides without disturbing the sample.
iv. The surplus soil at both the ends is trimmed and the weight of the cylinder with soil is determined.
v. Then, from the known dimension of the cutter, the volume and the moisture content of the soil is determined.
vi. The dry density of the soil is then computed using the following formula:
Bulk Density (γ t ) = (W 2 – W 1 ) / V
Dry Density (γ d ) = γ t / ( 1 + W)
W 1 = Weight of cutter
W 2 = Weight of the soil + cutter
W 2 – W 1 = Weight of soil
V = Volume of the cutter
Observation and Calculations
|Sl. No.||Observations and Calculations||Determination No.|
|1||Core cutter No.|
|4||Mass of empty core cutter (M1)|
|5||Mass of core cutter with soils (M2)|
|6||M=M2 – M1|
|7||The volume of cutter V|
|9||Dry density using formula|
Results of Core Cutter Method
Dry density of the soil= ________g/ml.
Advantages of Core Cutter Method
1. This method is relatively fast and simple.
2. Core cutter test can be carried out in the natural environment without sampling disturbance.
3. It is highly suitable for the dry density determination of cohesive soil as well as soft, fine-grained soils.
Disadvantages of Core Cutter Method
1. This method is only practicable at places where the surface of the soil is exposed and the cutter can be easily driven.
2. It is not suitable for cohesionless soil.
Precautions Taken While Performing Core Cutter Method
a. Soil around the core cutter should be removed before lifting the core cutter. This is done to minimize the disturbances.
b. This test should be performed only on fine-grained cohesive soils.
c. Core cutter should be driven into the ground till the steel dolly penetrates the ground halfway only so as to avoid compaction of the soil in the core.
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