Code of practice for uniaxial jacking test for deformation modulus of rock

IS 7317 - Scope & Key Formulas (Clause 6.6)

Scope:

• Deals with displacement measurement beneath a circular loaded area on rock.
• Focuses on interpreting test data for displacement under load.

Key Formula (Clause 6.6):

Displacement (\delta) at depth (Z) beneath the center of a circular loaded area:

[ \delta = \frac{2 p (1 - v^2)}{E} \sqrt{R^2 + Z^2} - \frac{p Z (1+v)}{E \sqrt{R^2 + Z^2}} - 1 ]

Where:

• (\delta) = displacement in loading direction (mm)
• (p) = stress at loaded surface (use small 'p' as per amendment)
• (v) = Poisson's ratio of rock
• (E) = modulus of elasticity of rock
• (R) = radius of loaded area (m)
• (Z) = depth from loaded surface to measurement point (m)

Table: Rock Displacement (mm) vs Depth (m)

Extensometer Anchor Depths (Typical)

Notes:

• Use small 'p' for stress as per latest amendment.
• Formula assumes elastic behavior and isotropic rock properties.
• Useful for designing rock support and monitoring displacement in geotechnical engineering.

flowchart LR
    A[Load Applied] --> B[Circular Loaded Area (radius R)]
    B --> C[Stress p at surface

IS 7317: General Requirements & Test Site Selection

Key Specifications from Clauses:

• Site Selection:

  • Prefer testing in drifts, tunnels, or underground openings (Clause 2.4).
  • If unavailable, test near open excavation sides.
  • Prepare test site quickly, ideally within 15 days of selection (Clause 3.2).
  • For weather-sensitive rocks, test within 30 days of excavation to capture fresh rock properties.

• Information to Collect (Clause 2.5):

  • Rock Quality Designation (RQD)
  • Point Load Strength Index
  • Number, dip, strike, spacing, and condition of joint sets
  • Groundwater condition (dry to flowing)
  • Rock Mass Rating (RMR) and Rock Mass Quality (Q)
  • Elastic modulus of rock material
  • Special features (shear/fault zones)
  • Excavation method and blasting damage description

• Test Report Requirements (Clause 7.1):

  • Test location coordinates, drift number, chainage
  • Rock burden above site, test position (floor/roof/wall)
  • Time elapsed between excavation and testing
  • Loading direction and rock stratification orientation
  • Geological description with RMR and Q
  • In-situ stresses, test agency, apparatus details
  • Data tabulation, stress-deformation plots, creep factors
  • Plot of Ed/Er vs. RMR for deformation modulus selection

Important Table: Rock Mass Rating (RMR) Summary (Typical)

Conceptual Workflow Mermaid Diagram:

flowchart TD
    A[Select Test Site] --> B[Geologist & Engineer Survey]
    B --> C[Collect Data: RQD, Joints, Water, RMR

IS 7317: Preparation of Test Site – Key Points & Specifications

1. Site Selection & Geological Mapping (Clauses 2.1 & 2.5)

• Compile all surface and subsurface geological data.
• Prepare a 3D geological map showing micro-geology of rock mass.
• Record jointly by geologists and engineers:
  • Rock Quality Designation (RQD)
  • Point Load Strength Index
  • Number, dip & strike of joint sets
  • Joint spacing & condition
  • Groundwater condition (dry, damp, wet, dripping, flowing)
  • Rock Mass Rating (RMR) and Rock Mass Quality (Q)
  • Modulus of Elasticity of rock material
  • Special features (shear/fault zones)
  • Excavation method (controlled blasting, chiselling)
  • Damage description due to blasting

2. Site Preparation (Clause 3.2)

• Prepare the test area within 15 days of site selection.
• For weather-sensitive rocks, conduct tests within 30 days of excavation to capture fresh rock properties.

3. Preferred Test Locations (Clause 2.4)

• Conduct tests in drifts, tunnels, or underground openings.
• Alternatively, near sides of open excavations for foundations or abutments.

Important Formulas & Ratings (for reference)

flowchart TD
    A[Geological Data Compilation] --> B[3D Geological Mapping]
    B --> C[Joint & Rock Parameters Recorded]
    C --> D[Site Selection]
    D --> E[Test Site Preparation (within 15 days)]
    E --> F[Testing in Drifts/T

IS 7317: Test Setup and Equipment Key Points

Test Setup Selection (Clauses 4.1, 4.2 & 5.1)

• Preferred setup: Fig. 4 (most accurate technique).
• Alternatives: Fig. 2 or Fig. 3 if Fig. 4 is not feasible.
• Setup depends on:
  • Testing environment (small drift, tunnel, open trench).
  • Direction of test (vertical, horizontal, inclined).
  • Measurement location (bearing plate, outside loaded area, inside rock mass).

Equipment Specifications (Clause 2.5 & Fig. 2A)

• Steel Plate: Minimum 60 cm diameter, 2.5 cm thick.
• CI Plates: 75 cm thick with plane face.
• Hydraulic Jack: 200 tonnes capacity, calibrated.
• Dial Gauges:
  • 4 nos. with legs at 120° or 90° for fixing.
  • Least count: 0.002 mm.
• Face Preparation: Dressed parallel, coated with 5 mm cement mortar.
• Supporting Frame: Angle iron frame for jack support and easy positioning.

Summary Table of Equipment

flowchart LR
    A[Test Environment] --> B{Test Setup Choice}
    B -->|Preferred| C[Fig. 4 Setup]
    B -->|Alternate| D[Fig. 2 or 3 Setup]
    C & D --> E[Measurement & Equipment]
    E --> F[Steel Plate Ø ≥ 60cm, 2.5cm thick]
    E --> G[Hydraulic Jack 200t]
    E --> H[Dial Gauges (4 nos., 0.002mm)]
    E --> I[Face coated with 5mm cement mortar]

This ensures standardization and accuracy in uniaxial jacking tests per

IS 7317 - Test Procedure Key Points

1. Test Setups (Clause 4.2 & 5.1)

• Preferred Setup: Fig. 4 (most recommended for testing)
• Alternative Setups: Fig. 2 or Fig. 3 if Fig. 4 is not feasible
• Fig. 2B shows Uniaxial Jacking Equipment for narrow drifts and galleries (Clause 3.0)

2. Test Procedure (Clause 5)

• Follow the preferred test setup for accuracy.
• Use hydraulic jacks as per Clause 3.0 specifications.
• Ensure proper alignment and load application as per figures.

3. Formula Update (Page 9, Clause 6.6)

• The existing formula for load or stress calculation is replaced (exact formula not provided here).
• Always refer to the latest IS 7317 edition for the updated formula.

Typical Test Setup Summary:

flowchart LR
    A[Test Setup Selection] --> B{Is Fig. 4 setup possible?}
    B -- Yes --> C[Use Fig. 4 setup]
    B -- No --> D{Is Fig. 2 or Fig. 3 possible?}
    D -- Yes --> E[Use Fig. 2 or 3 setup]
    D -- No --> F[Modify setup accordingly]

For detailed dimensions and hydraulic jack specs, refer to Fig. 2B and related clauses in IS 7317.

IS 7317: Interpretation of Test Data (Clauses 5.8, 5.9, 6.6, 7.1)

Key Formula for Displacement (Clause 6.6)

Displacement ( \delta ) beneath a circular loaded area:

[ \delta = \frac{2P (1 - v^2)}{E} \sqrt{R^2 + Z^2} - \frac{PZ(1+v)}{E} \sqrt{R^2 + Z^2} ]

Where:

• ( \delta ) = displacement in loading direction (mm)
• ( P ) = stress at loaded surface
• ( v ) = Poisson's ratio
• ( E ) = modulus of elasticity
• ( R ) = radius of loaded area
• ( Z ) = depth below loaded surface

Important Data (Rock Displacement vs Depth)

Test Data Interpretation (Clause 5.8 & 7.1)

• Plot deformation vs stress, time, and depth to derive:

  • Modulus of deformation/elasticity at various stress levels
  • Creep factors
  • Variation of moduli with depth

• Test report must include:

  • Test location, rock mass description, in-situ stresses
  • Test setup details, equipment specs, and calibration
  • Tabulated data and plots (stress vs deformation, time vs deformation)
  • Calculated moduli and creep factors
  • Plot of ( E_d / E_r ) vs RMR for design modulus selection

Summary Diagram: Data Interpretation Flow

flowchart TD
    A[Test Setup & Execution] --> B[Data Collection]
    B --> C[Plot Deformation vs Stress/Time/Depth]
    C --> D[Calculate Modulus & Creep Factors]
    D --> E[

IS 7317: Reporting of Test Results — Key Points

Essential Report Contents (Clause 7.1)

• Test environment: drift or open rock surface.
• Test site location: 3D coordinates, drift number, chainage.
• Overburden extent above test site.
• Test position: floor, roof, or side walls.
• Time elapsed since excavation.
• Testing direction: vertical, horizontal, or inclined.
• Rock mass orientation & loading direction.
• Geological description including RMR and Q values.
• In-situ rock stresses.
• Testing agency details.
• Uniaxial apparatus specs, photos, accuracy, sensitivity.
• Tabulated raw data.
• Graphs: Stress vs deformation, Time vs deformation, Depth vs deformation.
• Deformation and elastic moduli at different stress levels.
• Creep factors per stress level.
• Additional relevant info.
• Plot of Ed/Er vs RMR for deformation modulus selection.

Key Formula: Displacement under Circular Loaded Area (Clause 6.6)

[ \delta = \frac{2P(1 - v^2)}{E} \left[ \frac{R}{\sqrt{R^2 + Z^2}} - 1 \right] + \frac{PZ(1+v)}{E \sqrt{R^2 + Z^2}} ]

• (\delta) = displacement (mm)
• (P) = stress at loaded surface
• (v) = Poisson's ratio
• (E) = modulus of elasticity
• (R) = radius of loaded area
• (Z) = depth from loaded surface

Creep Factor Calculation (Clause 6.7)

[ \text{Creep Factor} (%) = \frac{\text{creep deformation during load increase}}{\text{total deformation}} \times 100 ]

Typical Extensometer Anchor Depths (Example)

IS 7317: Application of Modulus of Deformation

Key Formula (Clause 4.3)

[ E_d = \frac{(1 - v) \times P \times m}{\delta \times A} ]

Where:

• (E_d) = Modulus of deformation (kg/cm²)
• (v) = Poisson's ratio (typical values:
  • 0.20 for granite/excellent rock
  • 0.25 for gneiss, quartzites
  • 0.30 for mica schist, slates)
• (P) = Total load on test plate (kg)
• (m) = Shape factor (0.96 for circular plate, 0.95 for square plate)
• (\delta) = Deformation in one loading cycle (cm)
• (A) = Area of test plate (cm²)

Elastic modulus (E_e) is calculated similarly using recoverable deformation instead of total deformation.

Important Notes:

• Modulus depends on stress level; use engineering judgment for design values (Clause 1.1).
• Based on Boussinesq solution for point load on infinite, homogeneous, isotropic, linear elastic material (Clause 6.5).
• Plot deformation vs. stress/time/depth for detailed analysis (Clause 5.8).

Typical Poisson's Ratio Values for Rocks:

flowchart TD
    A[Apply Load P] --> B[Measure Deformation δ]
    B --> C[Calculate Ed using formula]
    C --> D[Plot Ed vs Stress/Time/Depth]
    D --> E[Determine Design Modulus]

This method helps estimate in-situ rock mass deformation modulus for tunnel/drift stability analysis.

IS 7317 Key References & Specifications Summary

1. Modulus of Deformation (Clause 8.1)

• Ed: For static analysis of dam foundations, varies with stress levels.
• Ee: Dynamic modulus for dynamic analysis; often taken as elastic modulus at max stress.
• Use Ee for design of concrete linings in pressure tunnels/penstocks.

2. Important Notes on Modulus Application

• In-situ rock mass under confining pressure; lab tests usually without it → modulus increases with depth.
• Saturation reduces modulus drastically, especially in poor rocks → apply correction factors.
• Use 3D Finite Element Method for dam foundation settlement analysis.
• Plastic behavior → non-linear analysis recommended.

3. Amendments & Contact

• Amendments issued are listed in the document but none currently specified.
• BIS offices and contacts provided for further standards and clarifications.

Typical Formula (Example from Clause 6.6)

(Exact formula substitutions not provided in context, refer to IS 7317 for detailed equations)

Visual Reference

• Fig. 2, 3, 4: Typical test setups for rock mass modulus (Clause 4.2).

Summary Table: Application of Modulus of Deformation

flowchart TD
    A[Rock Mass] --> B[In-situ Conditions]
    B --> C{Confining Pressure?}
    C -- Yes --> D[Higher Modulus (Ed, Ee)]
    C -- No --> E[Lab Test Modulus]
    D --> F[Use in Design]
    E --> F
    F --> G{Saturation?}
    G -- Yes --> H[Apply Correction Factors]
    G -- No --> I[Use Direct Modulus]

For detailed formulas and amendments, consult the full IS 7317 document from BIS.