The core cutter method is a method used to determine the dry density of soil and 130 mm long and 100mm diameter cylindrical core cutters are used for testing the in-situ compaction of cohesive and clay soils.
Bulk density of the soil can be quickly calculated by using the core cutter method and dry density of the fill can be calculated by determining the moisture content of the soil and also the percentage of voids.
Without stones core cutter method is only used in fine-grained cohesive soils and used to determine the in-situ density of soil and also bulk density can be easily found by using the core cutter method. Also, the void percentage and dry density can be calculated.
The cutter is pressed into the soil mass for determination of the dry density of the soil and it is lifted up when filled with the soil.
The difference between core cutter method and sand replacement method is that in core cutter method density of soft soils like clay soil or other cohesive soils which are placed as fills are determined while in sand replacement method, a small pit is made and the soil that is excavated is weighed. The sand replacement method is known to be better than the core-cutter method.
The Formula for Dry Density:
The dry density is obtained by a formula as given below;
M is the mass of the wet soil in the cutter.
V is the internal volume of the cutter.
w is the water content.
Equipment for Core Cutter Method:
There are following equipment used in the core cutter method such as;
100mm internal diameter and 130mm long cylindrical core cutter.
Steel rammer with a mass of 9 kg and overall about 900mm of length with the foot and the staff.
The steel Dolley of 25mm high and internal diameter of 100 mm.
Accuracy of 1g weighing balance.
Palette knife, steel rule, and straight edge, etc.
The Procedure of Core Cutter Method:
There are several steps in the procedure of the core cutter method as given below;
To the nearest 0.25 mm determine the internal diameter and height of the core cutter.
To the nearest gram determine the mass M1 of the cutter.
Level the surface, about 300mm square in area, and expose a small area of the soil to be tested.
Over the top of the core cutter place the Dolley and into the soil mass using the rammer press the core cutter. When about 15mm of the Dolley protrudes above the soil surface then stop the pressing.
Remove the soil surrounding the core cutter and take out the core cutter and from the lower end of the cutter, the soil would project.
Then remove the Dolley and by using a straight edge trim the tip and bottom surface of the core cutter carefully.
To the nearest gram M2, Weigh the core cutter filled with the soil.
From the cutter remove the core of the soil and for the water, content determination takes a representative sample. Then determine the water content.
Observations and Calculations of Core Cutter Method:
Average of at least three determinations should be reported as shown in the table below;
Observations and Calculations
Core cutter number
M1, Mass of core cutter
M2, Mass of core cutter with soils
M = M2 – M1
V, Volume of the cutter
Dry density by using formula
The result of the dry density of the soil will be in g/ml.