Determination of Field Density of Soil by Core Cutter Method (IS-2720-Part-29)

 

Practical Manual: Determination of Field Density of Soil by Core Cutter Method (IS-2720-Part-29)

Aim:

To determine the field density of soil using the Core Cutter Method.

Reference:

• IS 2720-Part 29: Determination of dry density of soil in place by the core-cutter method.

Apparatus:

1. Cylindrical core cutter
2. Steel rammer
3. Steel dolly
4. Balance
5. Steel rule
6. Spade or pickaxe
7. Straight edge
8. Knife

Procedure:

1. Preparation of Core Cutter:

   • Measure the height (H) and internal diameter (D) of the core cutter.
   • Apply a thin layer of grease to the inner surface of the core cutter.
   • Weigh the empty core cutter and record the weight as W₁.

2. Preparation of Soil Surface:

   • Clean and level the site where the soil density is to be determined.
   • Ensure the surface is free from debris and loose material.

3. Inserting the Core Cutter:

   • Place the steel dolly on top of the core cutter.
   • Using the steel rammer, drive the core cutter vertically into the soil until the steel dolly penetrates the ground halfway. This prevents soil compaction inside the core.

4. Lifting the Core Cutter:

   • Gently excavate the soil around the cutter using a spade or crowbar.
   • Carefully lift the core cutter without disturbing the soil inside it.

5. Trimming and Cleaning:

   • Trim the excess soil from the top and bottom surfaces of the core sample using a straight edge or knife.
   • Clean the outside surface of the core cutter.

6. Weighing the Soil Sample:

   • Weigh the core cutter containing the soil sample and record the weight as W₂.

7. Moisture Content Determination:

   • Eject the soil from the core cutter and take a representative sample to determine the moisture content of the soil.

Precautions:

1. This method is suitable only for fine-grained soils like silts and clays. Coarse-grained soils may not provide accurate results due to difficulty in obtaining undisturbed samples.
2. The core cutter should only be driven into the soil until the steel dolly penetrates halfway, to avoid compaction inside the cutter.
3. Remove the surrounding soil carefully before lifting the core cutter to minimize disturbances in the sample.

Observations and Calculations:

To calculate the wet unit weight (γₓₓₓₓₓ) of the soil, use the following formula:

$$γ_{wet} = \frac{{W₂ - W₁}}{V}$$

Where:

• W₁ = Weight of the empty core cutter
• W₂ = Weight of the core cutter with the soil sample
• V = Volume of the core cutter = $\frac{\pi D² H}{4}$
• D = Internal diameter of the core cutter
• H = Height of the core cutter