Methods of test for soils, Part 41: Measurement of swelling pressure of soils

IS 2720 Part 41: Scope & Key Specifications

Scope:
This part covers the Swelling Pressure Test by Consolidometer Method to determine swelling characteristics of soil.

Key Specifications & Formulas

• Specimen Size:

  • Standard diameter: 60 mm
  • Alternatives: 50, 70, 100 mm (special cases)
  • Initial thickness as per sample

• Soil Sample Details:

  • Visual description
  • Liquid limit (LL) & Plasticity Index (PI)
  • % soil fraction < 0.002 mm
  • Specific gravity (G)

• Density & Moisture Content Calculations:

• Pressure Increments for Test:

Data Recording Forms (Appendix A)

• Form 1: Soil & specimen details, natural density

IS 2720 Part 41: Constant Volume Method for Swelling Pressure

Key Apparatus:

• Consolidometer cell with porous stones (top & bottom)
• Direct strain measuring dial gauge
• Brass cap (perforated)
• Loading platen/anvil

Procedure Summary:

• Soil specimen is placed in a rigid cell preventing volume change.
• Swelling pressure is measured as the load applied to prevent volume increase.
• After swelling, consolidation is done by applying incremental pressures until original volume is restored.

Important Tables & Data Sheets:

Key Formulas:

• Wet Density, ρ_w
  [ \rho_w = \frac{\text{Weight of wet soil}}{\text{Volume of soil sample}} ]

• Dry Density, ρ_d
  [ \rho_d = \frac{\text{Weight of dry soil}}{\text{Volume of soil sample}} ]

• Moisture Content, w (%)
  [ w = \frac{\text{Weight of water}}{\text{Weight of dry soil}} \times 100 ]

• **Swelling Pressure, P

IS 2720 Part 41 - Apparatus and Equipment for Swelling Pressure Test (Constant Volume Method)

Key Apparatus Components:

• Consolidometer Cell: Rigid, minimizes volume change.
• Top & Bottom Porous Stones: Ensure drainage while restraining soil.
• Loading Anvil/Platen: Applies pressure on soil specimen.
• Direct Strain Measuring Dial Gauge: Measures deformation.
• Brass Cap (Perforated): Holds specimen in place.

Important Specifications:

• Soil specimen contained in a rigid ring/container with known diameter and thickness.
• Use of constant volume ensures swelling pressure is measured without volume change.
• Apparatus should minimize leakage and volume change.

Key Tables from Appendix A & Form 2:

Key Formulas:

• Wet Density (ρ_w):
  [ ρ_w = \frac{\text{Weight of wet soil}}{\text{Volume of soil specimen}} ]

• Dry Density (ρ_d):
  [ ρ_d = \frac{\text{Weight of dry soil}}{\text{Volume of soil specimen}} ]

• **Moist

IS 2720 Part 41: Preparation of Soil Specimen

Key Points from Clauses:

• Undisturbed Soil Specimens (Clause 8.1 & 4.1):
  Specimens should be collected during the driest months (April-June) to maximize swelling pressure. Handle specimens delicately to avoid disturbance, especially due to thin consolidation rings and desiccated soil.

• Disturbed Soil Specimens (Clause 8.2 & 4.2):
  Soil is compacted in a standard Proctor mould at desired field density and water content. Specimens are then cut to size as per undisturbed specimen guidelines.

Important Specifications:

Typical Procedure Summary:

1. Undisturbed: Extract soil core carefully, avoid disturbance.
2. Disturbed: Compact soil in Proctor mould to target density and moisture.
3. Trim samples to required size carefully.

Formula for Dry Density (ρ_d):

[ \rho_d = \frac{W_s}{V} = \frac{W \times 100}{(w+100) \times V} ]

Where:

• (W_s) = weight of solids (g)
• (W) = weight of wet soil (g)
• (w) = water content (%)
• (V) = volume of specimen (cm³)

flowchart TD
    A[Soil Sample] --> B{Type of Sample}
    B -->|Undisturbed| C[Collect in dry season]
    B -->|Disturbed| D[Compact in Proctor mould]
    C --> E[Trim specimen carefully]
    D --> E
    E --> F[Test specimen for swelling pressure]

This ensures maximum swelling pressure and accurate test results per IS 2720 Part 41.

IS 2720 Part 41: Swelling Pressure Test by Consolidometer Method – Key Test Procedure Details

1. Soil Sample & Specimen Details (Appendix A)

• Soil Sample:
  • Visual description
  • Liquid Limit (LL), Plasticity Index (PI)
  • % of soil fraction < 0.002 mm
• Specimen:
  • Undisturbed or remoulded
  • Specific gravity (G)

2. Natural Density & Moisture Content Calculations

3. Specimen Dimensions (Clause 3.1.1)

• Diameter: 60 mm (alternatively 50, 70, 100 mm for special cases)
• Initial thickness: recorded before test

4. Swelling Pressure Test Data (Form 2)

IS 2720 Part 41: Calculations and Report for Swelling Pressure Test

Key Data to Record (Appendix A, Clause 6.1)

• Soil Sample Details:
  • Visual description
  • Liquid limit & Plasticity index
  • % soil fraction < 0.002 mm
• Soil Specimen Details:
  • Undisturbed/remoulded
  • Specific gravity

Natural Density & Moisture Content Calculations

Swell-Compression Test Data (Form 2)

• Compression dial readings recorded until steady state.
• Loads applied until specimen returns to original volume.

Reporting

• Use IS:2-1960 rounding rules.
• Present all observations in prescribed forms (Appendix A).
• Include all calculated parameters with units.

flowchart TD
    A[Soil Sample Details] --> B[Prepare Specimen]
    B --> C[Measure Natural Density & Moisture]
    C --> D[Swelling Pressure Test]
    D --> E[Record Compression & Thickness Change]
    E --> F[Calculate Parameters]
    F --> G[Prepare Report per IS 2720 Part 41]

This ensures standardized, clear presentation of swelling pressure test results.

IS 2720 Part 41: Key Details & Specifications for Soil Specimen

1. Soil Specimen Details (Clause 6.1, Appendix A)

• Soil sample description:
  • Visual description
  • Liquid limit & Plasticity index
  • % soil fraction < 0.002 mm
• Specimen type: Undisturbed or remoulded
• Specific gravity (G) of soil

2. Specimen Dimensions (Clause 3.1.2)

• Thickness (h): ≥ 20 mm
• Minimum thickness: ≥ 10 × max grain diameter
• Diameter to thickness ratio (D/h): ≥ 3

3. Natural Density & Moisture Content Calculations

4. Swelling Pressure Test (Form 1 & 2)

• Use High Sensitive Proving Ring (200 kg capacity) for load measurement.
• Pressure increments and corresponding compression/thickness changes recorded as per table:

flowchart TD
    A[Soil Sample] --> B[Visual Description]
    B --> C[Liquid Limit & Plasticity Index]
    C --> D[Particle Size < 0.002 mm]
    D --> E[Prepare Specimen]
    E --> F[Dimension Check: Thickness ≥ 20mm, D/h ≥ 3]
    F -->

IS 2720 Part 41: Recording & Observations for Swelling Pressure Test

Key Points from Clause 6.1 & Appendix A

• Forms for Recording:
  • Form 1: Soil & specimen details, natural density, moisture content, swelling dial readings at time intervals.
  • Form 2: Pressure increments vs compression and change in thickness of specimen.

Important Data to Record (Form 1)

Pressure Increment Table (Form 2)

Notes on Observations

• Record swelling dial readings under seating load 5 kN/m² at specified time intervals.
• Use Form 1 for swelling pressure test data and Form 2 for swell-compression data

IS 2720 Part 41: Assembly and Setup Key Points

Assembly Setup (Clause 5.1.2 & 9.1.2)

• The soil specimen assembly is mounted on the loading frame ensuring axial load transmission via the loading cap.
• The proving ring tip must contact the consolidation cell without eccentricity.
• A direct strain dial gauge is attached to measure swelling/compression.
• Specimen is inundated with distilled water before swelling.

Key Data & Calculations (Clause 6.1 & Appendix A)

Typical FORM 2 Pressure Increment Table (for Swell-Compression Test)

Summary

IS 2720 Part 41 — Data Analysis & Interpretation Key Points

1. Specimen Details & Properties

• Specimen Diameter: Standard 60 mm (50, 70, 100 mm allowed in special cases) [Clause 3.1.1]
• Soil Properties to record:
  • Visual description
  • Liquid Limit (LL) & Plasticity Index (PI)
  • % soil fraction < 0.002 mm
  • Specific gravity (G)
  • Undisturbed or remoulded

2. Natural Density & Moisture Content Calculations

3. Swelling Pressure Test Data (Consolidometer Method)

• Pressure increments (kgf/cm² and kN/m²):

• Record compression and change in thickness at each pressure increment.

4. Reporting & Rounding

• Follow IS 2-1960 for rounding off final values [Clause 0.5].

flowchart TD
    A[Soil Sample] --> B[Measure Properties]
    B --> C{Calculate

IS 2720 Part 41: Forms for Recording Test Data (Swelling Pressure Test)

Key Forms (Appendix A):

Form 1: Swelling Pressure Test by Consolidometer Method

• Soil Sample Details:
  • Visual description
  • Liquid limit & Plasticity index
  • % soil fraction < 0.002 mm
• Soil Specimen Details:
  • Undisturbed/remoulded
  • Specific gravity
• Natural Density & Moisture Content:

• Swelling Dial Readings: Recorded at elapsed times under seating load of 5 kN/m² (0.05 kgf/cm²).

Form 2: Data Sheet for Swell-Compression Test

IS 2720 Part 41: Key Details & Formulas for Soil Sample and Test Results

1. Soil Sample Details (Clause 6.1 & Appendix A)

• Visual Description: Texture, color, structure.
• Atterberg Limits:
  • Liquid Limit (LL)
  • Plasticity Index (PI)
• Particle Size: % soil fraction < 0.002 mm (clay content).
• Soil Specimen Type: Undisturbed or remoulded.
• Specific Gravity (G): Typically 2.6 - 2.8 for mineral soils.

2. Natural Density & Moisture Content

Where:

• (W) = weight,
• (V) = volume of soil sample (from container dimensions).

3. Swelling Pressure Test (Consolidometer Method)

• Use these increments to plot swelling pressure vs. deformation.
• High Sensitive Proving Ring: 200 kg capacity (Clause 7.10) for load measurement.

4. Specimen Preparation

• Undisturbed samples: Follow Clause