Engineering Technology

The Field Dry Density Test is conducted to determine the in-situ dry density of soil at a particular location. It's a crucial part of geotechnical engineering used in road construction, embankments, earth dams, and other earthwork projects to ensure proper compaction. Here are the key details:

Purpose of the Test

To determine the dry density of compacted soil in the field, and compare it with the maximum dry density obtained from the laboratory Proctor compaction test.

Common Methods

1. Sand Replacement Method (most widely used)

2. Core Cutter Method (for cohesive soils)

3. Water Displacement Method (for rocky terrain or coarse-grained soils)

4. Nuclear Density Gauge (modern and fast, but needs special licensing)

1. Sand Replacement Method (IS 2720 Part 28)

Apparatus:

Sand pouring cylinder

Calibrated sand (uniform and dry)

Metal tray with a central hole

Balance

Digging tools

Procedure:

1. Calibrate the apparatus by finding the weight of sand that fills the cone.

2. Level the soil surface and place the tray.

3. Dig a hole of known volume.

4. Collect the excavated soil and weigh it.

5. Fill the hole with sand from the cylinder and weigh the amount used.

6. Calculate the volume of the hole from the sand used.

7. Determine the water content of excavated soil.

8. Compute the dry density using:

Dry Density = Weight of soil from hole / Volume of hole X 100 / 100 + Moisture Content (%)

2. Core Cutter Method (IS 2720 Part 29)

Apparatus:

Core cutter (steel cylinder)

Rammer

Balance

Straight edge

Procedure:

1. Drive the core cutter into the soil.

2. Remove and trim excess soil.

3. Weigh the cutter with soil.

4. Find the volume of the cutter.

5. Determine moisture content.

6. Calculate dry density similarly.

Typical Uses

Earthworks and road construction

Checking field compaction during embankment construction

Quality control in civil engineering projects.