The dry density of soil is an important factor for determining the compactness of the soil. the field density test are conducted for determining the in place density of soil. The dry density of a soil sample is typically related to the presence of voids in the given sample under a given condition. The relation between the water content and dry density is inversely proportional to a certain extend this is because the dry density increases with the decrease in the water content.
There are various methods that are used for dry density for field density test. some of these are enumerated below.
- determination of dry density of soil in place by core cutter method.
- determination of dry density of soil in place by ring and water replace method.
- determination of dry density of soil in place by rubber balloon method.
- determination of dry density of soil in place by sand replacement method.
here we are going to discuss about how to determine the dry density by field density test by with the help of core cutter method. One of the disadvantage of this method is that is not considered to be accurate, however it is typically conducted for quick field density test results of soil.
TO DETERMINE DRY DENSITY OF SOIL BY CORE CUTTER METHOD
A core cutter is typically a cylindrical seamless steel tube for determination of the dry density of soil. In the of field density test, the cutter is pressed into the soil mass so that it is filled with the soil and when The cutter filled with the soil it is lifted up. The mass of the soil in the cutter is determined.
(IS-2720-Part-29-Determination of dry density of soil in place by the core-cutter method. The dry density is obtained as)
M= mass of the wet soil in the cutter
V= internal volume of the cutter
w= water content.
Apparatus for Determination of the Dry Density of Soil :-
1. Cylindrical core cutter having dimension of 100mm internal diameter and 130mm long.
2. Steel rammer, mass 9kg, overall length with the foot and staff about 900mm.
3. Steel dolley, 25mm high and 100mm internal diameter
4. Weighing balance, accuracy 1g.
5. Palette knife
6. Straight edge, steel rule etc
Procedure for Field Density Test
1. Determine the internal diameter and height of the core cutter to the nearest 0.25mm
2. Determine the mass (M1) of the cutter to the nearest gram.
3. Now an exposed area of 300 sq. mm is taken where the field density is to be determined and level the surface.
4. After leveling the surface place the dolley over the top of the core cutter and press the core cutter vertically down the soil mass using the rammer.
5. Continue pressing when about 15mm of the dolley protrudes above the soil surface.
6. Remove the soil surrounding the core cutter, and take out the core cutter. Soil would project from the lower end of the cutter.
6. Remove the dolley and trim the tip and bottom surface of the core cutter carefully using a straight edge.
7. Weigh the core cutter filled with the soil to the nearest gram (M2).
8. Now remove the core of the soil from the cutter. Take a representative sample for the water content determination.
9. Determine the water content as in IS 2720 Part II 1973.
Observation and Calculations:
|Sl. No.||Observations an 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||Volume of cutter V|
|9||Dry density using formula|
Dry density of soil= ________g/ml.
It is necessary to make repeated determination and to average them for the accurate results of field density test since the dry density varies from point to point.