Code of practice for in-situ vane shear test for soils

IS 4434: Scope & Key Specifications for Vane Shear Test Instrument

Scope Highlights

• Instrument must apply torque through the rod string and measure it accurately.
• Angular rotation reading device required at the upper end of the extension rod.
• Torque applicator speed control to maintain 0.1º/s rotation rate.
• Friction of torque applicator should be negligible and checked periodically.

Key Table: Selection of Torque Applicator (Table 1)

• Torque applicator capacity considered: 600 kgf.cm (60 N.m)
• Larger shear strengths require smaller vane sizes (37.5 & 50 mm).

Important Formula (Clause 5.2.1)

For vane height ( H = 2D ) (where ( D ) is vane diameter):

[ S = \frac{3M}{11D^3} \times 10^3 \quad \text{(S in kgf/m²)} ]

• ( M ) = Torque applied (kgf.cm)
• ( D ) = Vane diameter (cm)

Summary Diagram

flowchart TD
    A[Apply Torque M] --> B[Measure Angular Rotation]
    B --> C[Calculate Shear Strength S]
    C --> D[Use formula: S = (3M)/(11D³) × 10³]
    D --> E[Select Torque Applicator from Table 1]

References:

• IS 4434 Clause 2.1.2.1 & Table 1
• IS 4434 Clause 5.2.1 formula for shear strength calculation
• Torque applicator speed: 0.1º/s

IS 4434: Apparatus & Equipment for Vane Shear Test

Key Specifications:

• Torque Applicator Capacity: 60 N·m (600 kgf·cm) standard.
• Rotation Speed: Controlled at 0.1º/s.
• Friction: Should be negligible; check periodically.
• Angular Rotation Measurement: Required at the upper end of the extension rod.
• Jacking Arrangement: For pushing shoe and vane where required.
• Calibration: Apparatus must be checked and calibrated as needed.

Important Table: Selection of Torque Applicator (Clause 2.1.2.1)

Additional Notes:

• Extension pipe connections and flushing holes are provided as per Fig. 2 (Typical Vane Protecting Shoe).
• Maintain test records per Appendix A format.
• Apparatus calibration and friction checks are essential for accuracy.

Formula for Torque (T):

[ T = \tau \times A \times r ]

Where:

• ( \tau ) = shear strength (kN/m²)
• ( A ) = area of vane (m²)
• ( r ) = radius of vane (m)

This ensures correct selection and operation of equipment for reliable vane shear testing.

IS 4434: Procedure of Testing - Key Points

1. Records & Documentation (Clause 4.1)

• Maintain detailed records of vane shear tests using Appendix A proforma.
• Include all relevant test data for traceability.

2. Torque Applicator Specifications (Clause 2.1.2.1 & Table 1)

• Torque applicator must:
  • Apply torque through rods to the vane.
  • Measure torque and angular rotation.
  • Control rotation speed at 0.1º/s.
  • Have negligible friction (periodically checked).
• Select torque applicator capacity based on estimated soil shear strength:

3. Test Procedure Notes

• Final test values should be rounded off as per IS 2-1960.
• Calibration of apparatus is mandatory before testing.
• Use Figure 2 for vane protecting shoe details during testing.

Summary Flow of Testing Procedure

flowchart TD
    A[Prepare Vane & Apparatus] --> B[Calibrate Torque Applicator]
    B --> C[Insert Vane in Soil]
    C --> D[Apply Torque at 0.1º/s]
    D --> E[Record Torque & Rotation]
    E --> F[Calculate Shear Strength]
    F --> G[Record & Round Off Results]

This ensures reliable and standardized vane shear test results as per IS 4434.

IS 4434: Recording of Vane Shear Test Results — Key Points

1. Record Keeping (Clause 4.1 & Appendix A):

• Maintain detailed records using the recommended proforma including:
  • Bore-hole details, soil log, water level, driving resistance notes.
  • Vane test details: apparatus number, vane size, torque conversion factor.
  • Test parameters: depth of vane tip, time to failure, max torque, revolutions for remoulding.
  • Shear strength values for undisturbed and remoulded soil, and sensitivity.
  • Any deviations from standard procedure with reasons.

2. Torque Applicator Selection (Table 1):

3. Computation and Rounding (Clause 5):

• Round off test results per IS 2-1960, matching significant digits to those specified in the standard.

Example: Shear Strength Calculation

[ \text{Shear Strength} (kN/m^2) = \frac{T}{K \times A} ]

Where:

• (T) = Maximum torque (N·m)
• (K) = Conversion factor (depends on equipment)
• (A) = Area of vane (m²), for a rectangular vane (A = 2 \times \text{length} \times \text{width})

Proforma Snapshot (Simplified)

IS 4434 - Key Computation Formulas and Tables for Vane Shear Test

1. Computation Formula (Clause 5.2.1)

For vane shear test when H = 2D (H = height, D = diameter of vane):

[ S = 3 \times 10^6 \times \left(\frac{M}{11 \times D^3}\right) \times 10^3 \quad \text{(S in kgf/m}^2\text{)} ]

• S = Shear strength
• M = Torque applied (N·m or kgf·cm)
• D = Diameter of vane (m or cm)

Notes:

• Use consistent units for M and D.
• Round off results as per IS 2-1960 guidelines.

2. Torque Applicator Selection (Table 1)

• Torque applicator capacity: 600 kgf·cm (60 N·m)
• Rotation speed: 0.1º/s
• Friction must be negligible and checked periodically.

3. Test Records

Maintain records as per Appendix A proforma, including:

• Torque applied
• Angular rotation
• Vane dimensions
• Soil type and depth

flowchart TD
    A[Vane Shear Test] --> B[Apply Torque M]
    B --> C[Measure Angular Rotation]
    C --> D[Calculate Shear Strength S]
    D --> E[Use formula: S = 3×10^6 × (M / 11D³) × 10³]
    E --> F[

IS 4434: Recommended Proforma & Key Specifications for Vane Shear Test Records

1. Proforma for Test Records (Clause 4.1 & Appendix A)

Maintain detailed records including:

• Bore-hole No., Soil Log, Ground Elevation
• Method of hole formation and water level
• Vane test apparatus No., Vane size, Dummy rod diameter
• Conversion factor for torque equipment
• Depth of vane tip below bore-hole bottom
• Time to failure, maximum torque reading
• Number of revolutions for remoulding
• Shear strength of undisturbed and remoulded soil (kN/m² or kgf/cm²)
• Sensitivity (ratio of undisturbed to remoulded shear strength)
• Record deviations from standard procedure

2. Key Formula for Shear Strength (τ) Calculation

[ \tau = \frac{T}{K} ]

Where:

• ( T ) = Maximum torque applied (N·m)
• ( K = \pi \times D^2 \times H / 2 ) (torque factor depending on vane dimensions)
• ( D ) = Vane diameter (m)
• ( H ) = Vane height (m)

3. Torque Applicator Selection (Table 1, Clause 2.1.2.1)