Methods of test for soils, Part 40: Determination of free swell index of soils

IS 2720 Part 40 - Scope & Key Formula

Scope:
This part of IS 2720 deals with the determination of the free swell index of soil, which indicates the swelling potential when soil is immersed in water.

Key Formula for Free Swell Index (FSI)

[ \text{Free swell index, %} = \frac{V_a - V_x}{V_x} \times 100 ]

Where:

• ( V_a ) = Volume of soil specimen in distilled water (free swell volume)
• ( V_x ) = Volume of soil specimen in kerosene (original volume)

Kerosene is used as a non-polar liquid that does not cause soil swelling.

Specifications:

• Use graduated measuring cylinders for volume readings.
• Kerosene and distilled water cylinders should be used for volume measurements.
• Volumes are read directly from the cylinders.

Summary Table

flowchart LR
    A[Soil Sample] --> B{Measure Volume}
    B -->|In Kerosene| C[Vx (Original Volume)]
    B -->|In Distilled Water| D[Va (Swelled Volume)]
    C --> E[Calculate FSI]
    D --> E
    E --> F[FSI = ((Va - Vx)/Vx) * 100%]

For detailed procedures, refer to IS 2720 Part 40 (1977).

IS 2720 Part 40 (1977) — Key Formula & Specifications for Free Swell Index

Free Swell Index Calculation

The free swell index (FSI) measures soil volume increase when immersed in water relative to kerosene (non-swelling liquid).

[ \boxed{ \text{Free swell index, %} = \frac{V_a - V_x}{V_x} \times 100 } ]

• ( V_a ) = Volume of soil specimen in distilled water (free swell volume)
• ( V_x ) = Volume of soil specimen in kerosene (original volume)

Important Notes:

• Kerosene is used as it does not cause swelling.
• Graduated cylinders must be accurately calibrated for volume readings.
• The test is useful for assessing swelling potential of soils.

Reference:

• IS: 2720 (Part XL) - 1977 specifies apparatus and procedure.
• Use graduated cylinders with clear volume markings.

Summary Table

flowchart LR
    A[Soil Sample] --> B{Place in Graduated Cylinder}
    B --> C1[Kerosene Cylinder (Vx)]
    B --> C2[Distilled Water Cylinder (Va)]
    C1 --> D[Read Volume Vx]
    C2 --> E[Read Volume Va]
    D & E --> F[Calculate Free Swell Index]

For detailed apparatus specs and procedural steps, consult full IS 2720 Part 40 (1977) document.

IS 2720 Part 40 — Apparatus Specifications & Key Formula

Apparatus:

• Glass Graduated Cylinders: Two cylinders, each with 100 ml capacity as per IS: 878-1956.
• One cylinder is filled with kerosene (non-polar liquid to prevent soil swelling).
• The other cylinder is filled with distilled water.

Key Formula:

Calculate the Free Swell Index (FSI) of soil as:

[ \text{Free Swell Index (%)} = \frac{V_a - V_x}{V_x} \times 100 ]

Where:

• ( V_a ) = Volume of soil in distilled water cylinder (free swell volume)
• ( V_x ) = Volume of soil in kerosene cylinder (original soil volume)

Notes:

• Kerosene prevents swelling, so ( V_x ) represents the original soil volume.
• Distilled water causes swelling, so ( V_a ) represents swollen volume.

Summary Table:

This setup ensures precise measurement of soil swelling characteristics as per IS 2720 Part 40 (1977).

IS 2720 Part 40 (1977) covers Sampling and Sample Preparation for soil testing. Although the code text isn't provided, key points generally include:

Sampling

• Representative Sampling: Collect samples from multiple locations to represent the soil mass.
• Sample Size: Depends on test type; typically 2-5 kg for mechanical tests.
• Avoid Contamination: Use clean tools and containers.

Sample Preparation

• Air-Drying: Spread soil thinly to air dry at room temperature.
• Sieving: Use a 4.75 mm sieve to separate coarse particles.
• Grinding: For fine soil, gently crush lumps without altering particle size.
• Mixing: Homogenize the sample thoroughly before testing.

Typical Table: Sample Preparation Steps

Note: Follow specific test requirements for moisture content and sample size.

flowchart LR
    A[Collect Soil Sample] --> B[Air Dry Sample]
    B --> C[Pass through 4.75 mm Sieve]
    C --> D[Crush Lumps if Needed]
    D --> E[Mix Thoroughly]
    E --> F[Ready for Testing]

This ensures consistent, reliable soil test results per IS 2720 Part 40.

IS 2720 Part 40 (1977) — Test Procedure Key Points

This part covers the Determination of Free Swell Index of Soils.

Key Specifications & Test Procedure

• Sample Preparation: Use oven-dried soil passing 425 µm sieve.
• Test Setup: Place soil in a graduated cylinder with distilled water.
• Measurement: Record initial soil volume (V₀) and volume after 24 hrs immersion (V₁).

Key Formula

[ \text{Free Swell Index (FSI)} = \frac{V_1 - V_0}{V_0} \times 100 ]

Where:

• (V_0) = Initial volume of soil (ml)
• (V_1) = Volume of soil after 24 hrs immersion (ml)

Rounding Off

• Final results should be rounded as per IS 2:1960 guidelines.

Typical Table for Interpretation of FSI

flowchart TD
    A[Prepare soil sample] --> B[Place in cylinder with water]
    B --> C[Record initial volume V₀]
    C --> D[Wait for 24 hours]
    D --> E[Record final volume V₁]
    E --> F[Calculate FSI = ((V₁ - V₀)/V₀)*100]
    F --> G[Interpret swelling potential]

This procedure helps assess soil expansiveness critical for foundation design.

IS 2720 Part 40 - Calculation of Free Swell Index

The key formula for calculating the Free Swell Index (FSI) of soil is:

[ \text{Free Swell Index, %} = \frac{V_a - V_x}{V_x} \times 100 ]

Where:

• ( V_a ) = Volume of soil specimen in distilled water (free swell volume)
• ( V_x ) = Volume of soil specimen in kerosene (original soil volume)

Notes:

• Kerosene is used as it is non-polar and does not cause soil swelling, thus representing the original volume.
• Distilled water causes swelling, so the volume read is the free swell volume.
• Graduated cylinders must be used as per IS 2720 Part 40 specifications.

Summary Table: Free Swell Index Calculation

flowchart LR
    A[Soil Sample] --> B{Place in Kerosene}
    B --> C[Measure Volume \(V_x\)]
    A --> D{Place in Distilled Water}
    D --> E[Measure Volume \(V_a\)]
    C & E --> F[Calculate Free Swell Index]
    F --> G[FSI = ((\(V_a - V_x\))/\(V_x\)) * 100]

This method helps assess soil expansiveness critical for foundation design and earthworks.

IS 2720 Part 40 (1977) - Key Formulas & Specifications for Free Swell Index

Free Swell Index Calculation (Clause 4.1)

[ \text{Free Swell Index (%)} = \frac{V_a - V_x}{V_x} \times 100 ]

• (V_a) = Volume of soil specimen in distilled water (free swell volume)
• (V_x) = Volume of soil specimen in kerosene (original volume)

Kerosene is used as it does not cause soil swelling (non-polar liquid).

Specifications

• Graduated Cylinders: Used for volume measurements of soil in kerosene and distilled water.
• Volumes are read directly from the cylinder.
• Results rounded off as per IS 2:1960 guidelines.

Reporting

• Report the Free Swell Index in percentage.
• Mention the test method and any rounding applied.

Summary Table

flowchart LR
    A[Soil Sample] --> B{Place in Kerosene}
    A --> C{Place in Distilled Water}
    B --> D[Read Volume \(V_x\)]
    C --> E[Read Volume \(V_a\)]
    D --> F[Calculate Free Swell Index]
    E --> F
    F --> G[Free Swell Index % = \(\frac{V_a - V_x}{V_x} \times 100\)]

For detailed procedures and cylinder specifications, refer to IS 2720 (Part 40) - 1977.

IS 2720 Part 40 - Notes and Precautions Summary

Key Formula:

The Free Swell Index (FSI) is calculated as:

[ \text{Free Swell Index, %} = \frac{V_a - V_x}{V_x} \times 100 ]

• (V_a) = Volume of soil specimen in distilled water (free swell volume)
• (V_x) = Volume of soil specimen in kerosene (original volume)

Important Notes:

• Kerosene is used as a non-polar liquid to avoid soil swelling, representing the original soil volume.
• Distilled water causes swelling; volume read here is the free swell volume.
• Graduated cylinders must be kerosene and distilled water resistant, calibrated as per IS 2720 (Part XL) - 1977.
• Rounding off of results must follow IS 2-1960 guidelines.
• This test helps assess soil expansiveness, critical for foundation design.

Precautions:

• Ensure no air bubbles in soil during volume measurement.
• Use clean, calibrated graduated cylinders.
• Read volume levels at the bottom of meniscus.
• Perform tests at consistent temperature to avoid volume variation.

flowchart LR
    A[Soil Sample] --> B{Place in Kerosene}
    B --> C[Read Volume \(V_x\)]
    A --> D{Place in Distilled Water}
    D --> E[Read Volume \(V_a\)]
    C --> F[Calculate FSI using formula]
    E --> F

This ensures accurate free swell index determination as per IS 2720 Part 40.