Methods of Test for Soils, Part 29: Determination of Dry Density of Soils In-place by the Core-cutter Method

IS 2720 Part 29: Scope & Key Specifications for Soil Dry Density Determination (Core-Cutter Method)

Scope (Clause 0.1)

• Establishes procedure for in-place dry density determination of soil using the core-cutter method.
• Applicable for field density tests on cohesive and granular soils.

Apparatus Dimensions (Clause 2.2 & Fig.1)

• Steel Dolley:
  • Height: 2.5 cm
  • Internal Diameter: 10 cm
  • Wall Thickness: 7.5 mm
  • Lip to fit on core-cutter
• Core Cutter:
  • Diameter: 25 mm (solid mild steel staff)
  • Hardened cutting edge, corner rounded
  • Tolerance on essential dimensions: ±0.25 mm

Reporting & Recording (Clause 5.1, 5.2 & Appendix A)

Key Formulas

[ \text{Bulk Density}, \quad \rho_{bulk} = \frac{W_s - W_c}{V_c} ]

[ \text{Water Content}, \quad w = \frac{W_2 - W_3}{W_3 - W_1} \times 100 ]

[ \text{Dry Density}, \quad \rho_{dry} = \frac{\rho_{bulk} \times 100}{100 + w} \

IS 2720 Part 29: Apparatus for Determination of Water Content

• Reference Apparatus: As per Clause 2.10, apparatus for water content determination must comply with IS 2720 Part 2 (1973).

• Key Equipment Includes:

  • Weighing balance: Accuracy ±0.01 g.
  • Drying oven: Capable of maintaining 105 ± 5°C.
  • Containers: Moisture cans or crucibles made of non-corroding material.
  • Desiccators: For cooling samples post drying.

• Additional Apparatus for In-place Density (Rubber Balloon Method):

  • Rubber balloon device with calibrated volume.
  • Measuring cylinder or container for water.
  • Rigid frame or apparatus to hold the balloon in place.

Recommended Proforma (Clause 5.1, Appendix A)

Water Content Formula:

[ w = \frac{W_w - W_d}{W_d} \times 100 ]

Where:

• ( w ) = Water content (%)
• ( W_w ) = Weight of wet soil sample (g)
• ( W_d ) = Weight of dry soil sample (g)

flowchart LR
    A[Soil Sample] --> B[Weigh Wet Sample]
    B --> C[Dry in Oven at 105 ± 5°C]
    C --> D[Cool in Desiccator]
    D --> E[Weigh Dry Sample]
    E --> F[Calculate Water Content]

This summarizes the apparatus and procedure per IS 2720 Part 29 for water content determination.

IS 2720 Part 29 (1975) – Sampling and Procedure: Key Points

IS 2720 Part 29 deals with Sampling of soils for engineering purposes. Although the code text is not fully provided, the standard outlines:

Sampling Procedure:

• Representative Sampling: Samples must represent the soil strata without disturbance.
• Sample Types: Disturbed, undisturbed, and block samples depending on test requirements.
• Sample Size: Sufficient quantity for required tests, typically 2-5 kg for disturbed samples.
• Sampling Tools: Augers, split spoon samplers, thin-walled tube samplers (Shelby tubes) for undisturbed samples.

Key Formulas (General Soil Sampling Context):

• Bulk Density, ρb = W / V
  Where W = weight of soil sample, V = volume of sample.

• Moisture Content, w = (Ww / Wd) × 100%
  Ww = weight of water, Wd = dry soil weight.

Typical Sampling Specifications:

flowchart LR
    A[Soil Strata] --> B[Sampling]
    B --> C{Sample Type}
    C --> D[Disturbed]
    C --> E[Undisturbed]
    C --> F[Block Sample]
    D --> G[Auger, Spade]
    E --> H[Shelby Tube]
    F --> I[Excavation]

For detailed procedures and equipment specs, refer directly to IS 2720 Part 29 (1975).

IS 2720 Part 29 - Key Calculations for Soil Density Determination

1. Bulk Density (y)

[ y = \frac{W}{V} ]

• W = mass of soil (oven-dried)
• V = volume of soil (core-cutter volume)

2. Water Content (w)

[ w = \frac{W_w}{W_d} \times 100 ]

• W_w = mass of water in soil
• W_d = mass of dry soil

3. Dry Density (ρ_d)

[ \rho_d = \frac{y}{1 + \frac{w}{100}} ]

Apparatus Dimensions (Clause 2.2 & Fig.1)

• Steel Dolley: Height = 2.5 cm, Internal diameter = 10 cm, Wall thickness = 7.5 mm
• Core-cutter: Diameter = 25 mm (±0.25 mm tolerance)
• Hardened cutting edge, rounded corners

Notes:

• Record results as per Appendix A proforma.
• Round numerical values as per revised IS rules.
• All dimensions in mm.

flowchart LR
    A[Soil Sample] --> B[Core Cutter Volume (V)]
    A --> C[Mass of Wet Soil (W_wet)]
    C --> D[Oven Dry Soil Mass (W_d)]
    B & D --> E[Calculate Bulk Density (y = W_d/V)]
    D & C --> F[Calculate Water Content (w = (W_wet - W_d)/W_d * 100)]
    E & F --> G[Calculate Dry Density (ρ_d = y / (1 + w/100))]

This summarizes the essential formulas and apparatus specs for soil density tests per IS 2720 Part 29.

IS 2720 Part 29: Reporting of Results (Core Cutter Method)

Key Formulas

• Bulk Density, ( \rho ): [ \rho = \frac{W_s - W_c}{V_c} \quad \text{(g/cm}^3\text{)} ] where:

  • ( W_s ) = Weight of core cutter + wet soil (g)
  • ( W_c ) = Weight of core cutter (g)
  • ( V_c ) = Volume of core cutter (cm³)

• Water Content, ( w ) (%): [ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100 ] where:

  • ( W_1 ) = Weight of container + lid (g)
  • ( W_2 ) = Weight of container + lid + wet soil (g)
  • ( W_3 ) = Weight of container + lid + dry soil (g)

• Dry Density, ( \rho_d ): [ \rho_d = \frac{\rho \times 100}{100 + w} \quad \text{(g/cm}^3\text{)} ]

Reporting Requirements (Clause 5.2)

• Dry density to 2 decimal places (g/cm³)
• Water content to 2 significant figures (%)

Recommended Tabular Format (Appendix A)

IS 2720 Part 29: Recommended Proforma for Recording Dry Density Test Results (Core Cutter Method)

Key Formulas:

• Bulk Density (ρ):
  [ \rho = \frac{W_s - W_c}{V_c} \quad \text{(g/cm}^3\text{)} ]
  where:
  (W_s) = Weight of core-cutter + wet soil (g)
  (W_c) = Weight of core-cutter (g)
  (V_c) = Volume of core-cutter (cm³)

• Water Content (w %):
  [ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100 ]
  where:
  (W_1) = Weight of container + lid (g)
  (W_2) = Weight of container + lid + wet soil (g)
  (W_3) = Weight of container + lid + dry soil (g)

• Dry Density (ρ_d):
  [ \rho_d = \frac{\rho}{1 + \frac{w}{100}} \quad \text{(g/cm}^3\text{)} ]

Recommended Tabular Proforma (Appendix A):