Methods of test for soils, Part 2: Determination of water content

IS 2720 Part 2: Scope - Key Specifications & Formulas

• Scope Reference: Definitions per IS 2809-1972 apply for soil testing.

• Soil Specimen Preparation:

  • Use IS sieves of sizes:
    425 µm, 2 mm, 4.75 mm, 9.50 mm, 19 mm, 37.5 mm (Clause 4.1a).
  • Refer IS 460 (Part I)-1978 for sieve specifications.

• Scoop Size for Sampling:
  About 20 cm long × 10 cm wide (Clause 9.7).

• Water Content Determination Formula:

[ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100% ]

Where:

• (W_1) = Mass of container (g)

• (W_2) = Mass of container + wet soil (g)

• (W_3) = Mass of container + dry soil (g)

• Pro Forma for Water Content Test:

This scope defines the standard approach for soil sampling, sieve sizes, and water content determination essential for geotechnical investigations per IS 2720 Part 2.

IS 2720 Part 2 (1973) - Key References, Formulas & Specifications

1. Test Sieves Sizes (Clause 4.1 & 16.1)

• Standard sieve sizes used:
  • 425 μm, 2 mm, 4.75 mm, 9.50 mm, 19 mm, 37.5 mm
• For detailed sieve specifications, refer to IS 460 (Part I) - 1978: Specification for test sieves: Part I Wire cloth test sieves.

2. Water Content Determination Formula (Clause 7.2)

3. Notes on Testing

• For bulky samples, place sample in chamber and absorbent in cup.
• For clayey soils/pastes, add 3 smaller + 1 bigger steel balls with absorbent for moisture meter tests.
• Procedure for moisture meter shaking and reading stabilization is detailed in Clause 28.4.

4. Additional References

• Definitions per IS 2809-1972 apply.
• Rounding off results as per IS 2-1960.
• Rapid moisture determination methods included (infra-red lamp, calcium carbide gas pressure).

flowchart TD
    A[Soil Sample] --> B{Weighing}
    B -->|Wet| C[Container + Wet Soil (W2)]
    B -->|Dry| D[Container + Dry Soil (W3)]
    E[Container Weight (W1)] --> F[Calculate Water Content]
    C --> F
    D --> F
    F --> G[Water Content w = ((W2 - W3) / (W3 - W1)) * 100%]

Summary: Use IS 460 for sieve specs; apply water content formula above; follow notes for sample handling and moisture meter use;

IS 2720 Part 2 (1973) - Definitions Key Points

• Definitions: Refer to IS 2809-1972 for all soil testing definitions as per Clause 2.0.

• Sieve Sizes (Clause 4.1): Standard IS sieve sizes used for soil grain size analysis:

  • 425 μm (micron) IS Sieve
  • 2 mm IS Sieve
  • 4.75 mm IS Sieve
  • 9.50 mm IS Sieve
  • 19 mm IS Sieve
  • 37.5 mm IS Sieve

• Note: For detailed sieve specifications, refer to IS 460 (Part I) - 1978 (wire cloth test sieves).

Water Content Calculation (Clause 7.2)

Water content, w (%) is calculated as:

[ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100% ]

Summary Diagram of Water Content Test

flowchart TD
    A[Weigh container (W1)] --> B[Add wet soil, weigh (W2)]
    B --> C[Dry soil in oven]
    C --> D[Weigh container + dry soil (W3)]
    D --> E[Calculate water content w = (W2 - W3)/(W3 - W1) * 100%]

References:

• IS 2809-1972 for definitions
• IS 460 (Part I) - 1978 for sieve specifications
• IS 2720 (Part 2) - 1973 for water content test procedure and pro forma

This ensures standardized terminology and testing methods for soil moisture content and grain size analysis.

IS 2720 Part 2 (1973) - Apparatus and Equipment for Water Content Determination

Key Equipment Specifications:

• Metallic Pressure Vessel with clamp for scaling cup and gauge calibrated in % water content (Clause 26.1, Fig. 3).
• Torsion Balance Moisture Meter:
  • Scale: 0-100% water content, with 0.2% divisions.
  • Built-in magnetic damper for stability.
  • Components include wire grips, torsion wire, damping magnet, calibrated drum, and balance arm (Fig. 1 & 2).
• Infra-red Lamp:
  • Power: 250 W, 220-230 V, 50 Hz AC supply.
  • Adjustable voltage (via Variac knob) for heat control.
  • Thermometer graduated 40°C to 150°C for drying temperature monitoring (Clause 21.1.1).

Handling & Testing:

• Test samples must be kept in airtight containers to avoid moisture loss/gain (Clause 23.1).
• Results should be recorded as per the pro forma in Appendix A (Clause 7.2).

Summary Table of Equipment:

flowchart LR
    A[Sample Container] --> B[Pressure Vessel with Clamp]
    B --> C[Torsion Balance Moisture Meter]
    C --> D[Infra-red Lamp (250W)]
    D --> E[Temperature Control (Variac & Thermometer)]
    E --> F[Moisture Content Reading (0-100%)]

This setup ensures precise water content determination per IS 2720 Part 2 standards.

IS 2720 Part 2: Sampling and Preparation of Soil Specimens

Key Specifications:

• Representative Sampling: Specimen must represent the soil mass accurately.
• Specimen Size: Depends on particle size distribution and weighing accuracy.
• Drier Soil: Requires larger specimen quantity.
• Water Content Samples: Should be discarded after use, not reused.

Recommended Minimum Quantities (Mass in grams):

Note: Refer IS 460-1962 for sieve sizes.

Preparation Notes:

• Sand requires no special preparation.
• Coarse powders may be ground.
• Cohesive/plastic soils tested with steel balls in pressure vessels (~6 g sample).

Summary Diagram:

flowchart TD
    A[Soil Mass] --> B[Sampling]
    B --> C{Particle Size}
    C -->|<425 micron| D[Min 25 g]
    C -->|2 mm| E[Min 30-50 g]
    C -->|4.75 mm| F[Min 200 g]
    C -->|10 mm| G[Min 300 g]
    C -->|20 mm| H[Min 300-500 g]
    C -->|40 mm| I[Min 1000 g]
    B --> J[Preparation]
    J --> K[Sand: No prep]
    J --> L[Coarse powders: Grind]
    J --> M[Cohesive soils: Steel balls, 6 g sample]

This ensures representative, accurate soil specimens for testing per IS 2720 Part 2.

IS 2720 Part 2: Oven Drying Method - Key Points

Equipment (Clause 21.1.1)

• Infra-red lamp: 250 W, 220-230 V, 50 Hz AC supply.
• Temperature control: Variac knob to maintain drying temp ~110 ± 5℃.
• Thermometer: Range 40 to 150℃, for monitoring drying temperature.
• Balance: Torsion balance with magnetic damper, scale in 0.2% water content divisions.

Procedure (Clauses 11.1, 23.6)

• Weigh clean container with lid: W₁
• Add soil sample loosely, weigh with lid: W₂
• Dry soil in oven at 110 ± 5℃ for 24 h (lid removed).
• Cool in desiccator with lid on, weigh dried soil + container: Wₐ
• Maintain temperature carefully, avoid overheating (use white paper test).

Calculation of Water Content (Clause 12)

[ w = \frac{W_2 - W_a}{W_a - W_1} \times 100% ]

Where:

• ( w ) = water content (%)
• ( W_1 ) = weight of empty container with lid
• ( W_2 ) = weight of container + wet soil with lid
• ( W_a ) = weight of container + dry soil with lid

Important Notes

• For soils with gypsum or organics, dry at 60–80℃ for reliable results.
• Avoid overheating; brown paper indicates overheating.

flowchart TD
    A[Weigh empty container (W₁)] --> B[Add wet soil and weigh (W₂)]
    B --> C[Dry soil at 110 ± 5℃ for 24 h]
    C --> D[Cool in desiccator with lid]
    D --> E[Weigh dried soil + container (Wₐ)]
    E --> F[Calculate water content: w = ((W₂ - Wₐ) / (Wₐ - W₁)) × 100%]

This method ensures accurate determination of soil moisture content per IS 2720 Part 2.

IS 2720 Part 2: Rapid Moisture Determination Using Infrared Lamp

Key Equipment Specifications (Clauses 21.1, 21.1.1)

• Infrared lamp: 250 W, 220-230 V, 50 Hz, single phase.
• Temperature control: Variac control knob adjustable to maintain drying temperature ~110 ± 5℃.
• Thermometer range: 40 to 150℃, mounted in lamp housing.
• Balance: Torsion balance with magnetic damper, scale in water % from 1 to 100%, divisions of 0.2%.

Procedure Highlights (Clauses 23.5, 23.6)

• Sample weight: ~25 g evenly spread on pan.
• Switch on lamp, adjust variac to raise temperature to ~110℃.
• Monitor thermometer; keep temperature between 105℃ and 110℃ by adjusting variac.
• Weight loss corresponds to moisture content; pointer rises as water evaporates.

Moisture Content Calculation (General formula)

[ \text{Moisture %} = \frac{W_i - W_d}{W_i} \times 100 ]

• (W_i): Initial weight of sample
• (W_d): Dry weight after heating

Temperature Control Summary

flowchart LR
    A[Prepare Sample (~25g)] --> B[Place on Balance Pan]
    B --> C[Lower Infrared Lamp Housing]
    C --> D[Switch On Lamp & Adjust Variac]
    D --> E[Monitor Thermometer (105-110℃)]
    E --> F[Observe Pointer Rise (Water Loss)]
    F --> G[Calculate Moisture Content]

This method provides rapid moisture content estimation by weight loss under controlled IR heating per IS 2720 Part 2.

Calcium Carbide Gas Pressure Method (IS 2720 Part 2)

This method rapidly determines soil water content by measuring gas pressure from calcium carbide reacting with free water.

Key Points & Formula:

• Reaction:
  [ \text{CaC}_2 + 2H_2O \rightarrow C_2H_2 (gas) + Ca(OH)_2 ]

• Measurement:
  Gas pressure generated is proportional to water content in the soil sample.

• Water Content Calculation:
  From pressure gauge reading → % water on wet basis (m) → convert to dry basis (w):

  [ w = \frac{m}{100 - m} \times 100 ]

Equipment:

• Calcium Carbide: Absorbent to react with free water (Clause 26.4)
• Scoop: For measuring calcium carbide (Clause 26.3)
• Pressure Gauge: Calibrated scale to read gas pressure proportional to water content

Procedure Summary:

1. Place soil sample in sealed container.
2. Add measured calcium carbide.
3. Measure gas pressure after reaction stabilizes.
4. Read % water (wet basis) from gauge.
5. Convert to dry basis water content using formula.

Notes:

• Ensure proper calibration of pressure gauge.
• Use dry, uncontaminated calcium carbide.
• Suitable for rapid field moisture content estimation.

flowchart TD
    A[Soil Sample] --> B[Add Calcium Carbide]
    B --> C[Reaction Produces Gas]
    C --> D[Measure Gas Pressure]
    D --> E[Read % Water (Wet Basis)]
    E --> F[Convert to Dry Basis Water Content]

This method offers quick, reliable moisture content determination per IS 2720 Part 2.

IS 2720 Part 2 - Use of Torsion Balance Moisture Meter

Key Specifications & Setup

• Power: 230 V, single-phase, 50 Hz AC supply.
• Main Components:
  • Torsion wire (16), balance arm (11), calibrated drum (13), damping magnet (9), on-off switch (4), variac knob for heat control (22), thermometer (28).
• Sample Handling:
  • Keep samples in sealed containers to avoid moisture loss (Clause 23.1).
  • Use absorbent (calcium carbide) and steel balls as per soil type (Clause 28.3).

Operating Procedure (Clause 28.4)

1. Shake meter vigorously (5s) with gauge downwards.
2. Turn gauge upwards, tap to settle contents.
3. Repeat shaking and tapping 3 times.
4. After final inversion and shaking, hold horizontal at chest height.
5. Wait for needle to stabilize; reading shows % moisture on wet mass basis.

Notes on Steel Balls Usage

• Place 3 small balls with soil in cup; larger ball with absorbent in body.
• Rotate horizontally for 10s, rest 20s; repeat until reading stabilizes (4-8 min).

Summary Table: Moisture Meter Components

flowchart LR
    A[Sample Preparation] --> B[Place sample & absorbent]
    B --> C[Shake meter downwards 5s]
    C --> D[Turn gauge upwards & tap]
    D --> E[Repeat shaking & tapping 3 times]
    E --> F[Hold horizontal, wait for reading]
    F --> G[Read moisture % on dial]

This method ensures accurate moisture content determination per IS 2720 Part 2.

Calculation of Water Content (IS 2720 Part 2 and related parts)

Water content (w) is expressed as a percentage of the dry weight of the soil.

Key Formulas:

1. From moisture balance scale (Clause 24.1, IS 2720 Part 2):

[ w = \frac{m}{100 - m} \times 100 % ]

• m = water content on wet basis (%) from moisture balance.

2. From mass measurements (Clauses 6.1, 12.1, 18.1):

[ w = \frac{W_3 - W_2}{W_2 - W_1} \times 100 % ]

Where:

• (W_1) = mass of container (dish/tray) alone (g)
• (W_2) = mass of container + wet soil (g)
• (W_3) = mass of container + dry soil (g)

Notes:

• Dry soil mass = (W_2 - W_1)
• Water mass = (W_3 - W_2)
• Water content = (Water mass / Dry soil mass) × 100%

Summary Table:

flowchart LR
    W1[Container Mass (W1)]
    W2[Wet Soil + Container (W2)]
    W3[Dry Soil + Container (W3)]
    WaterMass[Water Mass = W2 - W3]
    DryMass[Dry Soil Mass = W3 - W1]
    WaterContent[Water Content, w = (Water Mass / Dry Soil Mass) × 100%]

    W1 --> DryMass
    W3 --> DryMass
    W2 --> WaterMass
    W3 --> WaterMass
    WaterMass --> WaterContent
    DryMass --> WaterContent

This method ensures accurate determination

IS 2720 Part 2: Precautions and Limitations Summary

Key Precautions:

• Sample Handling (Clause 23.1):
  Keep test samples in suitable containers to prevent moisture loss or gain from ambient conditions.

• Pressure Release (Clause 28.5):
  Release pressure slowly and away from the operator when removing the cup to avoid accidents.

• Cleaning:
  After testing, empty contents and clean the instrument with a brush to maintain accuracy.

Limitations:

• The moisture meter readings are affected by ambient humidity; hence, proper sample storage is critical.
• The instrument requires careful handling of the torsion balance components (see Fig. 1 & 2 for parts like wire grips, damping magnets, thermometer, etc.).

Recommended Recording:

• Use the pro forma in Appendix A for consistent documentation of test results (Clause 7.2).

Instrument Key Components (from Figures 1 & 2):

Moisture Content Calculation (General Formula):

[ \text{Moisture Content (%)} = \frac{\text{Loss in weight on drying}}{\text{Original weight of sample}} \times 100 ]

flowchart LR
    A[Sample Preparation] --> B[Place in Container]
    B --> C[Weigh Sample]
    C --> D[Heat Sample (Controlled by Variac)]
    D --> E[Measure Torque on Torsion Wire]
    E --> F[Calculate Moisture Content]
    F --> G[Record Results (Appendix A)]
    G --> H[Clean Instrument]

Summary: Follow strict sample handling, gradual pressure release, and proper instrument cleaning to ensure reliable moisture content determination as per IS 2720 Part 2.

IS 2720 Part 2: Recording and Reporting Water Content Test Results

Key Specifications (Clause 7.2 & related)

• Results must be suitably recorded using a recommended pro forma (Appendix A).
• Water content and test results are reported per Clause 7.1 and 7.2 for all methods (Sand-Bath, Alcohol, Infra-red).

Pro Forma for Recording Water Content (Clause 7.2)

[ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100 ]

Summary

• Water content (w) is the ratio of the mass of moisture to the mass of dry soil, expressed as a percentage.
• Use the pro forma table to systematically record all weights.
• Follow reporting guidelines from Clause 7.1 and 7.2 for consistency.

flowchart TD
    A[Start: Soil Sample] --> B[Weigh Container (W1)]
    B --> C[Add Wet Soil & Weigh (W2)]
    C --> D[Dry Soil Sample]
    D --> E[Weigh Container + Dry Soil (W3)]
    E --> F[Calculate Water Content]
    F --> G[Record Results in Pro Forma]

This ensures standardized, clear reporting for water content tests as per IS 2720 Part 2.

IS 2720 Part 2: Safety Measures Key Points

The code primarily focuses on soil particle size analysis, with safety embedded in test procedures:

Safety Measures (Clause 28.5)

• Pressure Release: Release pressure slowly and away from the operator.
• Clamp Screw: Open clamp screw carefully to avoid sudden ejection.
• Cleaning: After test, empty contents and clean the instrument with a brush to avoid contamination or injury.

Relevant Specifications

• Test Sieves Sizes:

  Sieve Size (mm)	IS Code Reference
  425 µm	IS: 460 (Part I)-1978
  2 mm	IS: 460 (Part I)-1978
  4.75 mm	IS: 460 (Part I)-1978
  9.50 mm	IS: 460 (Part I)-1978
  19 mm	IS: 460 (Part I)-1978
  37.5 mm	IS: 460 (Part I)-1978

• Test Sieves Specification: Wire cloth test sieves per IS: 460 (Part I).

General Recommendations

• Record test results as per Appendix A pro forma.
• Follow subsidiary sand-bath method (Section 2) carefully for temperature control.

flowchart LR
    A[Start Test] --> B[Apply Pressure]
    B --> C{Pressure Release?}
    C -->|No| B
    C -->|Yes| D[Release Slowly Away from Operator]
    D --> E[Open Clamp Screw Carefully]
    E --> F[Remove Cup & Empty Contents]
    F --> G[Clean Instrument with Brush]
    G --> H[Record Results]

Summary: Always prioritize slow, controlled pressure release and proper cleaning to ensure operator safety and test accuracy in IS 2720 Part 2 procedures.

IS 2720 Part 2: Annexures & Figures - Key Formulas and Specifications

1. Water Content Determination Formula (Clause 7.2)

[ w = \frac{W_2 - W_3}{W_3 - W_1} \times 100% ]

• (W_1) = Mass of container (g)
• (W_2) = Mass of container + wet soil (g)
• (W_3) = Mass of container + dry soil (g)
• (w) = Water content (%)

2. Pro Forma Table for Recording Test Results (Clause 7.2)

3. Sieve Sizes (Clause 4.1 and 16.1)

• Standard IS sieves for soil particle size analysis include:
  2 mm, 4.75 mm, 9.50 mm, 19 mm, 37.5 mm
• Refer IS:460 (Part I)-1978 for detailed sieve specifications.

4. Figures for Equipment (Torsion Balance Moisture Meter)

• Fig. 1 & 2 show components such as wire grips, damping magnet, balance arm, calibrated drum, variac knob for heat control, and thermometer bracket.

5. Sample Handling (Clause 23.1)

• Samples must be kept in airtight containers to prevent moisture loss or gain.

flowchart TD
    A[Collect Soil Sample] --> B[Weigh Container + Wet Soil (W2)]
    B --> C[Dry Soil Sample in Oven]
    C --> D[Weigh Container + Dry Soil (W3)]
    D --> E[Calculate Water Content \(w\)]
    E --> F[Record Results in Pro Forma Table]

**Summary