Method of determination for direct shear strength of rock joints

IS 12634: Scope - Key Specifications and Reporting Requirements

• Data Presentation (Clause 8.2.2):
  For each test, provide:

  • Data tables
  • Consolidation curves
  • Graphs of shear stress & normal displacement vs shear displacement (as per Fig. 2 & 3)

• Shear Strength Reporting (Clause 8.2.4):
  Include:

  • Graphs of peak and residual shear strength vs normal stress (see Fig. 4)
  • Derived shear strength parameters (cohesion c and angle of internal friction φ)

• Tabulation (Clause 8.2.3):
  Abstracted values of:

  • Peak & residual shear strength
  • Corresponding normal stress
  • Shear & normal displacement

• Definitions:
  Refer IS 11358:1987 for standard definitions related to soil testing.

Typical Shear Strength Parameters Reporting Table (Example)

Shear Strength Parameters Formula

[ \tau = c + \sigma \tan \phi ]

• τ = shear strength
• c = cohesion
• σ = normal stress
• φ = angle of internal friction

graph LR
A[Test Conducted] --> B[Data Tables]
A --> C[Consolidation Curves]
A --> D[Graphs: Shear Stress & Normal Displacement vs Shear Displacement]
D --> E[Fig. 2 & 3]

F[Shear Strength Determination] --> G[Graphs: Peak & Residual Shear Strength vs Normal Stress]
F --> H[Derived Shear Strength Parameters]
G --> I[Fig. 4]

This ensures comprehensive reporting and clarity in shear strength testing per IS 12634

IS 12634 - Referenced Standards: Key Specifications & Reporting

1. Reporting of Test Results (Clause 8.2.2, 8.2.3, 8.2.4):

• Provide data tables including shear stress, normal displacement, and shear displacement curves (see Fig. 2 & 3).
• Tabulate peak and residual shear strength with corresponding normal stress and displacements.
• Plot graphs of peak and residual shear strength vs normal stress and derive shear strength parameters (see Fig. 4).

2. Definitions:

• Use definitions as per IS 11358:1987 for consistency.

3. Use of Standard Mark:

• Products conforming to IS 12634 bear the BIS Standard Mark, ensuring quality and compliance under BIS supervision.

Summary Table for Shear Strength Reporting (Clause 8.2.3 & 8.2.4)

Typical Shear Strength Parameters

Shear strength parameters are derived from the Mohr-Coulomb criterion:

[ \tau = c + \sigma \tan \phi ]

• c = cohesion
• φ = angle of internal friction
• σ = normal stress
• τ = shear strength

graph LR
A[Normal Stress (σ)] --> B[Shear Strength (τ)]
B --> C[Peak Shear Strength (τ_peak)]
B --> D[Residual Shear Strength (τ_residual)]
C --> E[Plot τ_peak vs σ]
D --> F[Plot τ_residual vs σ]
E & F --> G[Derive c and φ]

For detailed test procedures, data presentation, and graphical formats, refer directly to IS 12634 figures and IS 11358 definitions.

IS 12634 Definitions Summary

• The definitions in IS 12634 refer to IS 11358:1987 (Clause 3.1). For precise terminology, consult IS 11358:1987, which covers soil shear strength test definitions.

Key Reporting & Data (Clauses 8.2.2 to 8.2.4):

• For each test, provide:
  • Data tables with consolidation parameters.
  • Graphs of shear stress and normal displacement vs shear displacement (see Fig. 2 & 3).
  • Tabulated peak and residual shear strength with corresponding normal stress and displacements.
  • Graphs of peak and residual shear strength vs normal stress.
  • Derived shear strength parameters (cohesion c and friction angle φ) shown graphically (Fig. 4).

Typical Shear Strength Parameters (from IS 11358 & general practice):

Shear Strength Envelope (Mohr-Coulomb):

[ \tau = c + \sigma \tan \phi ]

Reporting Table Example (Clause 8.2.3):

graph TD
A[Normal Stress (σ)] --> B[Shear Strength (τ)]
B --> C[Peak Shear Strength (τ_peak)]
B --> D[Residual Shear Strength (τ

IS 12634: Test Equipment for Direct Shear Tests on Rocks

Key Specifications:

• Shear Box Assembly (Fig. 1): Includes specimen carrier, encapsulating material, and low friction arrangement.
• Force Measurement:
  • Normal and shear forces must be measured independently.
  • Accuracy: ±1% of maximum force during test.
  • Equipment must be calibrated before testing; calibration charts must be included in the report.

Data Presentation (Clause 8.2.2):

• Provide tables and graphs showing:
  • Shear stress vs shear displacement
  • Normal displacement vs shear displacement
    (Refer to Figures 2 & 3 in the code)

Test Report Requirements (Clause 8.1):

• Schematic diagram and description of test equipment.
• Methods for specimen handling (packing, transport, storage, mounting).
• Testing procedure description.

Typical Data Table Format Example:

Calibration and Accuracy Formula:

[ \text{Accuracy} = \pm 1% \times F_{\max} ]

where (F_{\max}) is the maximum force recorded during the test.

flowchart LR
    A[Shear Box Assembly] --> B[Specimen Carrier]
    A --> C[Encapsulating Material]
    A --> D[Low Friction Arrangement]
    E[Force Measurement] --> F[Normal Force Sensor]
    E --> G[Shear Force Sensor]
    F & G --> H[Calibration ±1% Accuracy]
    H --> I[Data Acquisition System]

This ensures reliable, reproducible shear test results per IS 12634.

IS 12634: Specimen Preparation Key Points

1. Specimen Protection (Clause 4.1)

• Use waterproof materials (wax, protective packing) to maintain moisture and prevent mechanical damage during cutting and transit.
• Use binding wire or metal bands to hold the specimen intact.

2. Mounting Equipment (Clause 4.3)

• Use specimen carriers that are detachable parts of test equipment.
• Use mixing utensils and strong encapsulating materials such as cement, plaster, or resin for secure mounting.

3. Displacement Measurement Devices (Clause 4.4.4)

• Use micrometer dial gauges or displacement transducers.
• Include calibration data for transducers in the test report.

4. Reporting (Clause 8.2.2)

• Provide data tables, consolidation curves, and graphs of shear stress and normal displacement vs. shear displacement.

flowchart TD
    A[Specimen Preparation] --> B[Protection: Waterproof packing, binding]
    A --> C[Mounting: Specimen carriers + encapsulating material]
    A --> D[Measurement: Displacement devices with specified accuracy]
    A --> E[Reporting: Data tables + graphs]

This ensures specimen integrity and accurate displacement measurement for reliable shear testing.

IS 12634: Test Procedure Key Points

• Test Report Requirements (Clause 8.1):

  • Include schematic diagram & description of test equipment.
  • Detail specimen handling: taking, packing, transporting, storing, mounting.
  • Describe the testing method clearly.

• Data Presentation (Clause 8.2.2):

  • Provide data tables, consolidation curves.
  • Graphs of shear stress (T) and normal displacement vs shear displacement (refer Fig. 2 & 3).
  • Non-linear peak strength curve can be correlated as per IS 11315 (Part 4):1987.

• Equipment Accuracy (Clause 4.4.3):

  • Normal and shear force measurement accuracy: ±1% of max force.
  • Equipment must be calibrated; calibration charts included in report.

• Strength Parameters (Clause 7.5):

  • Plot peak and residual shear strength vs normal stress (Fig. 4).
  • Determine parameters:
    • ( p_a ) (atmospheric pressure)
    • ( \phi_b ) (peak angle of internal friction)
    • ( \phi_r ) (residual angle of internal friction)
    • ( c ) (cohesion)
    • ( c' ) (effective cohesion)

Typical Shear Strength Relation (Fig. 4)

[ T = c + \sigma \tan \phi ]

Where:

• ( T ) = shear stress
• ( \sigma ) = normal stress
• ( c ), ( \phi ) = cohesion and friction angle (peak or residual)

Summary Table for Test Report

graph TD
A[Test Specimen] --> B[Testing Equipment]
B --> C[Measure Normal & Shear Forces]
C --> D[Data Acquisition]
D --> E[Plot She

IS 12634: Calculation and Presentation of Results

Key Specifications (Clauses 8.2.2 to 8.2.4):

• Data Presentation:

  • Tabulate test data including shear stress, normal displacement, shear displacement.
  • Plot curves of shear stress & normal displacement vs shear displacement (Fig. 2 & 3).

• Abstracted Values:

  • Tabulate peak and residual shear strength with corresponding normal stress and displacements.

• Shear Strength Parameters:

  • Plot peak and residual shear strength vs normal stress (Fig. 4).
  • Determine shear strength parameters:
    • pa (atmospheric pressure)
    • φb (peak friction angle)
    • φr (residual friction angle)
    • c (peak cohesion)
    • c' (residual cohesion)

Typical Formulas for Shear Strength Parameters:

[ \tau = c + \sigma \tan \phi ]

Where:

• (\tau) = Shear strength (peak or residual)
• (c) = Cohesion (peak or residual)
• (\sigma) = Normal stress
• (\phi) = Angle of internal friction (peak or residual)

Summary Table for Reporting (Example):

Visualization (Shear Stress vs Normal Stress):

graph LR
A[Normal Stress, σ] --> B[Peak Shear Strength, τp]
A --> C[Residual Shear Strength, τr]
B --> D[Determine c and φ (peak)]
C --> E[Determine c' and φ' (residual)]

Note:

IS 12634: Reporting of Results - Key Points

1. Data Presentation (Clause 8.2.2)

• Provide data tables for each test.
• Include consolidation data.
• Plot shear stress and normal displacement vs shear displacement curves (see Fig. 2 & 3).

2. Shear Strength Parameters (Clause 7.5 & 8.2.4)

• Plot peak and residual shear strength (T) vs normal stress (σₙ) (see Fig. 4).
• Derive strength parameters:
  • pa (atmospheric pressure)
  • φb (peak friction angle)
  • φr (residual friction angle)
  • c (peak cohesion)
  • c' (residual cohesion)

3. Reporting Requirements (Clause 8.1)

• Include:
  • Schematic of test equipment
  • Specimen handling & mounting methods
  • Testing procedure description

4. Typical Shear Strength Relation (Fig. 4)

5. Formula for Shear Strength Envelope

[ T = c + \sigma_n \tan \phi ]

• Use separate envelopes for peak and residual strengths.

graph LR
A[Test Data Tables] --> B[Consolidation Data]
B --> C[Shear Stress vs Shear Displacement Curves]
C --> D[Plot Shear Strength vs Normal Stress]
D --> E[Derive Strength Parameters: c, c', φb, φr]
E --> F[Final Test Report]

Summary: Report test data comprehensively with tables, curves, and graphs. Derive and present shear strength parameters from plotted shear vs normal stress graphs to characterize soil behavior accurately.