Field Density of soil by the Core-Cutter Method.

 Field Density of soil by the Core-Cutter Method. 

 

Objective 

Determine the in-place (bulk) density and dry density of soil using a core cutter. Applicable to fine-grained soils (≥ 90 % passing 4.75 mm IS sieve), not recommended for stony soils. 

Reference 

IS 2720 (Part XXIX): 1975 — Determination of Dry Density of Soils In-place by the Core-Cutter Method.  

 

Apparatus (per IS) 

• Core cutter (seamless steel tube): 100 mm internal Ø, 130 mm long, wall 3 mm, one end bevelled (kept greased). 

• Steel dolly: 25 mm high, 100 mm internal Ø, thick wall with lip (fits over cutter). 

• Steel rammer: ~9 kg, foot 140 mm Ø × 75 mm high, staff overall length ~900 mm. 

• Balance (±1 g), steel rule, straight edge, palette knife, digging tools, water-content apparatus as per IS 2720 (Part 2).  

 

Symbols (masses/volume) 

• Vc = internal volume of cutter (cm³) — from measured Ø & length to 0.25 mm. 

• Wc= mass of empty cutter (g). 

• Ws= mass of cutter + wet soil (g).  

Step-by-step Procedure 

1. Measure & Weigh 

1. Measure the internal diameter and length of the cutter to 0.25 mm; compute Vc (cm³). 

2. Weigh the empty cutter, Wc to 1 g. Prepare test spot 

1. Expose and level ~30 cm × 30 cm area on the soil layer to be tested.  

3. Drive the cutter 

1. Place the dolly on the cutter; ram vertically with the rammer without rocking until only ~15 mm of the dolly protrudes above ground. Keep cutting edge sharp; don’t use in stony soils.  

4. Extract & trim 

1. Dig out the cutter carefully, leaving some soil projecting below. 

2. Trim both ends flush with a straight edge so soil is exactly level with cutter ends.  

5. Weigh wet sample 

1. Clean outside; weigh cutter + wet soil, Ws to 1 g.  

6. Moisture content 

1. Remove the soil core. Take a representative portion to determine water content ww as per IS 2720 (Part 2).  

7. Replicates 

1. Make at least three determinations at nearby points and average (so an additional test would not change the average significantly).  

 

Calculations (as per IS) 

1. Bulk density (wet), 𝛾 (g/cm³): 

$$𝛾=\frac{ws-wc}{vc\mathrm{<br>}\mathrm{<br>}}$$

 

2. Dry density, γd (g/cm³): 

$$d=\frac{𝛾}{1+w}$$

 

  

Reporting (per IS) 

• Dry density to 0.01 g/cm³ and water content to two significant figures; keep a record in the IS proforma. Note soil type and any deviations.  

 

Suitability & Notes 

• Best for well-compacted, fine-grained soils; less accurate than sand-replacement, used when speed is essential. 

• Keep the cutting edge sharp; avoid aggregates/stony soils.