How to Get More Results Out of Your Field Density Measurements/ INSITU DENSITY/ CORE CUTTING Method

 
Field density measurements/ INSITU DENSITY/ CORE CUTTING Method




Objective: 

To determine the in-situ density by (1) sand replacement method and (2) 
core cutter method. 


Theory: 
The in-situ density refers to the mass per unit volume of a soil in the 
undisturbed state or of a compacted soil in-place. During the construction of the 
compacted fills, it is standard practice to make in-situ determination of density of the soil 
after it is placed to ensure that the compaction effort has been adequate. 
Sand Replacement Method 
In sand replacement method a hole of specified diameter is excavated in the ground. The 
mass of the excavated soil is measured. The volume of the hole is determined by filling it 
with clean, uniform sand whose dry density is determined separately by calibration. 

Apparatus
1. Sand pouring cylinder (3-liter capacity), mounted above the pouring cone and 
separately by shutter 
2. Cylindrical calibrating container, with 10cm internal diameter and 15cm internal 
depth 
3. Metal tray with central hole of a diameter equal to the diameter of the pouring cone. 
4. Auger for excavating hole 
5. Balance, cans for water content determination 
6. Clean closely graded natural sand passing the 1mm IS sieve and retained on 600ȝm IS sieve.

Procedure 
(a) Calculation of the density of the sand: 
1. Fill the clean closely graded sand in the sand-pouring cylinder up to a height 10mm 
below the top. Determine the total initial mass of the pouring cylinder plus sand (M1). 
This total initial mass of the pouring cylinder should be maintained constant through 
out the test for which the calibration is used. 
2. Determine the volume (V) of the calibrating container. 
3. Place the sand pouring cylinder on the top of the calibrating container. Open the 
shutter and allow the sand to run out. Close the valve when no further movement of 
sand observed at the top. Remove the cylinder carefully and find its mass (M2). 
4. Place the sand pouring cylinder on the polythene sheet placed on the flat surface. 
Open the shutter and allow the sand to run out. Close the valve when no further 
movement of sand observed at the top. Weigh the pouring cylinder again, which gives 
(M3). 
5. Put the sand on the polythene sheet and the calibrating container back in to the sand pouring container. 

(b) Determination of the in-situ density of the soil : 

1. Clean and level the site at which the in-situ density is to be determined. Keep the tray 
on the leveled surface and excavate a circular hole 100 mm in diameter and 
approximately 150 mm in depth, and collect all the excavated soil in tray. Determine 
the mass (M) of the excavated soil. 
2. Remove the tray and place the sand pouring cylinder. The cylinder should have its 
constant mass (M1). Open the shutter and permit the sand to urn into the hole. Close 
the shutter when no further movement of sand is seen. Remove the cylinder and 
determine its mass (M4). 
3. Keep a representative sample of the excavated soil for water content determination.

Calculation
1. The mass of the sand filling the calibrating container (Mc) can be found by deducting 
the mass of sand filling the conical portion (Mc = M2-M3) from the mass of sand (M4
= M1-M2) filling the container and the cone. Since the volume of the container (V) is 
known, the density of the sand (ȡ) may be retained. 
2. The mass of the sand occupying the test hole (Ms) is equal to M5 minus the mass of 
sand occupying the conical portion (Mc). Where, M5=M1-M4. 
3. The volume of the hole dug in the field (V) can be obtained by dividing the mass Ms, 
by the density of sand. 
4. The in-situ density of soil (ȡ) is then obtained by dividing the mass of soil (M) by its 
volume (V). If the water content of the soil is determined, the dry density of the soil.

Apparatus
1. Cylindrical core cutter of steel, approximately 100 mm in diameter and 450 mm in 
height 
2. Steel dolly, 100 mm internal diameter, 25 mm high and 7.5 mm thick 
3. Steel hammer 
4. Palette knife, steel rule, straight edge, balance, oven etc.


Core Cutter Method 

A cylindrical core cutter is a seamless steel tube. For determination of the dry density of 
the soil, the cutter is pushed into the soil mass to fill it with soil. The cutter is than 
removed. The mass of the soil in cutter is determined. The dry density is obtained as
Apparatus
1. Cylindrical core cutter of steel, approximately 100 mm in diameter and 450 mm in 
height 
2. Steel dolly, 100 mm internal diameter, 25 mm high and 7.5 mm thick 
3. Steel hammer 
4. Palette knife, steel rule, straight edge, balance, oven etc.

Procedure 
1. Measure the inside dimension of the core cutter and calculate its volume (Vc). Weigh 
the core cutter without dolly (Mc). 
2. Clean and level the site at which the in-situ density is to be determined. Put the dolly 
on the top of the core cutter. Drive the assembly into the soil using the hammer. 
3. Dig out the core cutter from the soil, and allow some soil to project from the lower 
end of cutter. With the help of straight edge, trim flat the ends of the cutter. 
4. Weigh the cutter full of soil (M1). 
5. Keep some representative sample of the soil for water content determination. 

Calculations:
1. The mass of the soil in core cutter is (M1-Mc). The volume of the soil is the same as 
the volume of cutter (Vc). 
2. The in-situ density of the soil (ȡ) is given by W/V. If the water content of the soil is 
determined, the dry density of the soil can be obtained as,

PROMEGA