Code of practice for field instrumentation of swelling pressure in expansive souls code of practice for field instrumentation of swelling pressure in expansive soils

IS 11550: Scope & Key Specifications

• Scope (Clause 1.1):
  Field instrumentation for measuring swelling pressure in expansive soils, primarily for foundation design of single/double storey buildings and light structures.

• Units (SI Units) Used:

  Quantity	Unit	Symbol	Definition
  Length	metre	m
  Mass	kilogram	kg
  Time	second	s
  Force	newton	N	1 N = 1 kg·m/s²
  Pressure, stress	pascal	Pa	1 Pa = 1 N/m²
  Energy	joule	J	1 J = 1 N·m
  Power	watt	W	1 W = 1 J/s

• Rounding Off (Clause 0.4):
  Final test/analysis values must be rounded per IS 2-1960 rules, keeping the same significant digits as the specified value.

• Precautions for Dial Gauges (Clause 7.5):

  • Clean daily with a hairbrush.
  • Cover loosely with polythene to avoid dust.

Summary Diagram: Scope & Application

graph TD
  A[IS 11550] --> B[Field Instrumentation]
  B --> C[Swelling Pressure Measurement]
  C --> D[Expansive Soils]
  D --> E[Foundation Design]
  E --> F[Single/Double Storey Buildings]
  E --> G[Light Structures]

This code ensures reliable measurement of swelling pressure critical for safe foundation design in expansive soil conditions.

IS 11550 - Key References, Units & Specifications

• Scope: Field instrumentation for measuring swelling pressure in expansive soils for foundation design of light structures (Clause 1.1).

• Instrument Care (Clause 7.5):

  • Dial gauges must be cleaned daily with a hair brush.
  • Keep loosely covered with polythene to prevent dust.

• Units (SI System) Used in IS 11550:

• Rounding Off (Clause 0.4): Final values must be rounded per IS 2-1960, maintaining significant figures as per specified values.

Summary Diagram: Instrument Care & Units

graph TD
  A[Dial Gauges] --> B[Clean daily with hair brush]
  A --> C[Cover loosely with polythene]
  D[SI Units] --> E[Force (N = kg·m/s²)]
  D --> F[Pressure (Pa = N/m²)]
  D --> G[Energy (J = N·m)]
  D --> H[Power (W = J/s)]

This ensures accurate swelling pressure measurements and standardization in reporting results.

IS 11550: Apparatus and Equipment Key Specifications

1. Assembly Components (Clause 3.0)

• Rigid plate & chamber assembly
• Proving ring with dial gauge
• Dial gauge & magnetic base
• Guide frame for central & encasing pipe
• Reaction beam anchoring assembly
• Plate bucket auger
• Spiral auger (15 cm diameter with extension rod)

2. Rigid Plate & Chamber Assembly (Clause 3.1)

• Plate: Circular, 15 mm thick, 11.5 cm diameter
• Socket: 20 mm internal diameter, 40 mm height, welded centrally on plate, verticality ensured
• Pipe: Galvanized iron, 20 mm outside diameter, screwed into socket, length per measurement depth
• Chamber: 4 mm thick galvanized iron sheet, internal diameter to allow 3 mm gap around plate, height ≤ 15 cm
• Top cover: 4 mm thick GI sheet with central socket, 2 mm clearance for pipe

3. Dial Gauge Care (Clause 7.5)

• Clean daily with hair brush
• Keep loosely covered with polythene to prevent dust

4. SI Units & Definitions (Summary)

Diagram: Rigid Plate & Chamber Assembly Setup

graph TD
    Plate[15 mm thick plate, 11.5 cm dia]
    Socket[20 mm dia socket welded centrally]
    Pipe[20 mm OD galvanized iron pipe]
    Chamber[4 mm GI sheet chamber with 3 mm gap]
    TopCover[4 mm GI sheet top cover with socket]

    Plate --> Socket --> Pipe
    Pipe --> Chamber
    Chamber --> TopCover

Note: Follow IS 2-1960 for rounding off test results as per specified significant figures.

IS 11550 Key Specifications for Excavation of Pit & Borehole Installation

1. Pit Excavation (Clause 4.1)

• Dimensions: 1 m × 1 m × 0.25 m depth.
• Leveling: Pit bottom must be leveled perfectly.
• Borehole:
  • Diameter: 15 cm (spiral auger as per IS 10442-1983).
  • Verticality: Maintain using auger boring guide (IS 2720 Part 40-1977).
  • Depth: Reach desired test depth with extension rods.
  • Cleaning: Remove loose material and level the borehole base using a plate bucket auger (Fig. 2).

2. Plate Bucket Auger (Clause 3.6)

• Used for leveling borehole bottom.
• Refer Fig. 2 for dimensions and details (typically a flat plate with cutting edges).

3. Rigid Plate & Chamber Assembly (Clause 3.1)

4. Installation Procedure (Clause 5.1)

• Lower plate & chamber assembly into borehole; plate rests on base.
• Check verticality of central pipe with spirit level.
• Encase central pipe with 40 mm dia pipe; connect to chamber socket.
• Suspend encasing pipe with clamps for free plate movement.
• Attach guide clamp to central pipe.
• Place steel ball on plate recess, then proving ring and screw jack.
• Apply initial pressure ≤ overburden pressure.
• Fill pit with water to ground level.
• Zero proving ring dial; use dial gauge on central pipe to measure plate movement.

Summary Diagram of Setup

graph TD
    A[Pit 1m x

IS 11550: Installation of Test Assembly – Key Specifications & Formulas

1. Guide Frame (Clause 3.5)

• Use 5 mm wide × 3 mm thick steel flats.
• Provide semi-circular supports matching the diameter of the encasing pipe.
• Purpose: Maintain verticality of the central rod and prevent disturbances.
• Reaction beam & anchoring assembly per IS 1888-1982 (Load test on soils).

2. Test Pit and Borehole (Clause 4.1)

• Excavate a pit: 1 m × 1 m × 0.25 m (depth).
• Borehole diameter: 15 cm (using spiral auger per IS 10442-1983).
• Maintain verticality with auger boring guide (IS 2720 Part 40-1977).
• Clean and level borehole bottom before test.

3. Assembly Components (Clause 3.0)

• Rigid plate & chamber assembly.
• Proving ring with dial gauge.
• Dial gauge with magnetic base.
• Guide frame for central & encasing pipes.
• Reaction beam anchoring assembly.
• Plate bucket auger & spiral auger (15 cm diameter).

4. Anchoring Assembly (Clause 7.1)

• Must be rigid and immovable during the test to ensure accurate readings.

Summary Table

Mermaid Diagram: Test Assembly Setup

graph TD
    A[Pit Excavation 1x1x0.25m] --> B[Borehole 15cm dia]
    B --> C[Clean & Level Borehole Bottom]
   

IS 11550: Recording of Swelling Pressure — Key Points & Table Format

Procedure Summary (Clause 5.1 & 6.2)

• Lower the plate and chamber assembly carefully into the borehole.
• Ensure the circular plate rests on the borehole base; check verticality with spirit level.
• Central pipe encased in 40 mm pipe, suspended with clamps for free plate movement.
• Place steel ball on plate recess, then proving ring and screw jack.
• Apply initial pressure (≤ overburden pressure) via screw jack through proving ring.
• Fill pit with water up to ground level.
• Set proving ring dial to zero.
• Use dial gauge on central pipe to measure upward plate movement (heave) due to swelling.
• Record readings only after loading with screw jack until heave dial reading returns to initial reading (no volume change).

Table Format for Recording Swelling Pressure (Clause 6.2)

Key Formula

[ \text{Stress (N/mm}^2) = \frac{\text{Proving Ring Load (N)}}{\text{Plate Area (mm}^2)} ]

• Plate Area must be known from test setup.
• Heave (mm) = Dial gauge reading × Least count of dial gauge.

Notes:

• Ensure no volume change during each reading for accurate swelling pressure.
• Initial pressure applied should not exceed natural overburden pressure.

flowchart TD
    A[Lower Plate & Chamber] --> B[Check Verticality]
    B --> C[Place Steel Ball, Proving Ring & Screw Jack]
    C --> D[Apply Initial Pressure ≤ Overburden]
    D --> E[Fill Pit with Water]
    E --> F[Set Proving Ring Dial to Zero]
    F --> G[Load with Screw Jack until Heave Dial = Initial]
    G --> H[Record Proving Ring Reading & Heave]

This ensures precise measurement of swelling pressure per IS 11550.

IS 11550 - Clause 7.5: Precautions for Dial Gauges

• Cleaning: Dial gauges must be cleaned daily using a hair brush to remove dust and debris.
• Protection: Keep dial gauges loosely covered with polythene covers to prevent dust accumulation.
• Handling: Handle instruments carefully to maintain accuracy and avoid damage.

Relevant SI Units & Definitions (for instrumentation)

Summary Diagram of Precautions Workflow

flowchart TD
    A[Daily Cleaning] --> B[Use Hair Brush]
    B --> C[Remove Dust]
    C --> D[Cover with Polythene]
    D --> E[Protect Dial Gauge]

Note: Proper maintenance ensures reliability and accuracy of dial gauge readings essential for foundation instrumentation.

IS 11550: Maintenance and Calibration Key Points

• Dial Gauge Care (Clause 7.5):

  • Clean daily with a hair brush.
  • Keep loosely covered with polythene to prevent dust ingress.

• Dial Gauge & Magnetic Base Standard (Clause 3.3):

  • Must conform to IS 1888-1982 for accuracy and reliability.

• Rounding Off (Clause 0.4):

  • Final test/analysis values rounded per IS 2-1960.
  • Maintain same significant figures as specified values.

Important Units & Definitions (SI Units)

Summary Diagram: Maintenance Workflow for Dial Gauge

flowchart TD
    A[Start of Day] --> B[Remove Dial Gauge]
    B --> C[Clean with Hair Brush]
    C --> D[Check Calibration]
    D -->|If OK| E[Cover with Polythene]
    D -->|If Not OK| F[Recalibrate or Replace]
    E --> G[Use for Measurements]
    F --> G

Note: For detailed calibration procedures, refer to IS 1888-1982 and manufacturer's guidelines. Regular calibration ensures measurement accuracy critical for foundation instrumentation.

IS 11550: Data Interpretation and Reporting - Key Points

1. Units and Symbols (SI Units)

2. Instrument Care (Clause 7.5)

• Dial gauges must be cleaned daily with a hair brush.
• Keep gauges loosely covered with polythene to avoid dust accumulation.

3. Rounding Off (IS 2-1960)

• Final test or analysis values must be rounded off according to IS 2-1960.
• Retain the same number of significant digits as the specified value.

Summary Diagram: Data Reporting Workflow

flowchart TD
    A[Measurement] --> B[Data Cleaning & Validation]
    B --> C[Unit Conversion (SI Units)]
    C --> D[Calculation & Analysis]
    D --> E[Rounding Off (IS 2-1960)]
    E --> F[Reporting & Documentation]

Use SI units consistently and ensure proper instrument maintenance for accurate data interpretation and reporting.