Code of practice for in-situ determination of rock mass deformability using a flexible dilatometer, Part 1: volume change

Scope Summary from IS 12955 Part 1 (Clauses 7.4, 8.1, 8.2):

This part covers the reporting and testing requirements for rock deformation and strength parameters from borehole tests.

Key Reporting Requirements (Clause 8.1 & 8.2)

• Site-wide reporting:

  • Drilling details: agency, method, equipment.
  • Geotechnical logs: drill core, casing, groundwater, rock types.
  • Discontinuities within ±0.5 m of test sections (refer IS 11315).
  • Calibration method, equipment, and full calibration results.

• Per-test reporting:

  • Tabulated raw and corrected readings with depth.
  • Derived deformability parameters with assumptions.
  • Graphs of parameters vs. applied pressure.
  • Logs of deformability variation by depth/distance.

Calculations for Non-Linear Behaviour (Clause 7.4)

• Non-linear deformation is considered, typically requiring iterative or curve-fitting methods.
• Deformability parameters (e.g., modulus) are derived as functions of stress or pressure.

Typical Deformability Parameters Reported

Example: Reporting Table Format

flowchart TD
    A[Site Drilling] --> B[Geotechnical Logging]
    B --> C[Discontinuity Analysis]
    C --> D[Calibration & Testing]
    D --> E[Data Tabulation & Graphing]
    E --> F[Deformability Parameter Derivation]
    F --> G[Non-linear Behaviour Calculations]
    G --> H[

IS 12955 Part 1 references a comprehensive set of Indian Standards (IS 11315 Parts 1 to 11) for quantitative description of rock mass discontinuities, covering:

Key Notes:

• These standards provide methods and parameters essential for rock mass characterization in engineering projects.
• They guide field data collection and quantitative analysis of rock discontinuities.
• The BIS ensures quality and conformity through licensing and periodic revision.

Usage:

• Refer to these IS parts for detailed procedures and formulas on rock discontinuity measurement.
• Ensure using the latest editions and amendments from BIS.

flowchart LR
    A[IS 12955 Part 1] --> B[IS 11315 Part 1: Orientation]
    A --> C[IS 11315 Part 2: Spacing]
    A --> D[IS 11315 Part 3: Persistence]
    A --> E[IS 11315 Part 4: Roughness]
    A --> F[IS 11315 Part 5: Wall Strength]
    A --> G[IS 11315 Part 6: Aperture]
    A --> H[IS 11315 Part 7: Filling]
    A --> I[IS 11315 Part 8: Seepage]
    A --> J[IS 11315 Part 9: Number of Sets]
    A --> K[IS 11315 Part 10: Block Size]
    A --> L[IS 113

IS 12955 Part 1: Location of Test Site – Key Points

1. Selection of Drill Hole Location (Clause 3.1)

• Choose locations considering:
  • Rock quality variations
  • Depths of weathering
  • Design requirements of the structure

2. Reporting Requirements for Test Site (Clause 8.1)

• Drilling details: Agency, method, equipment
• Geotechnical logs: Drill core data, cased/cemented sections, groundwater levels, rock types, test section locations
• Discontinuities: Characteristics within test section ±0.5 m (per IS 11315 Part 1-11:1985)
• Calibration: Method, equipment, deviations from standard procedure, and full calibration results

3. Preparation of Test Site (Clause 4)

• Ensure proper site readiness before testing (details in Clause 4)

Summary Table: Essential Site Data to Record

This ensures test data reliability for structural design.

IS 12955 Part 1: Preparation of Test Site – Key Points

1. Site Preparation (Clause 3.2:4)

• Ensure test hole is drilled using approved methods and equipment.
• Maintain test sections with clear boundaries for testing.
• Protect the test hole from contamination or damage during preparation.

2. Drilling and Documentation (Clause 8.1)

Report the following for the entire site:

• Drilling details: agency, method, equipment.
• Geotechnical logs: drill core records, cased/cemented sections, groundwater levels, rock types.
• Discontinuities: characteristics within test sections and ±0.5 m (see IS 11315 Part 1–11).
• Calibration/testing methods: equipment used, deviations from standard procedures.
• Calibration results: full data and analysis.

3. Equipment (Clause 5.1)

• Use specialized drilling equipment capable of producing stable holes for testing.
• Equipment must allow for precise placement and measurement in test sections.

Typical Documentation Table (Example)

flowchart TD
    A[Start: Site Selection] --> B[Drilling Test Hole]
    B --> C[Logging & Documentation]
    C --> D[Calibration of Equipment]
    D --> E[Conduct Tests]
    E --> F[Record & Report Results]

Summary: Follow IS 12955 Part 1 clauses for drilling, logging, calibration, and documentation to ensure reliable site preparation for rock testing.

IS 12955 Part 1 — Test Equipment Key Points

Calibration Equipment (Clause 5.2)

• Use calibration cylinders with:
  • Internal diameter = test hole diameter
  • Length ≈ active probe length
  • Known elastic properties for accurate calibration

Pressure Measuring System (Clause 5.5.2)

• Use Bourdon gauge or electrical transducer
• Range: as required by test
• Reading sensitivity: better than ±2% of the range used

Test Procedure & Reporting (Clauses 4.3 & 8.2)

• Drill cores must be logged for:
  • Recovery percentage
  • Rock and joint characteristics
• Test reports must include:
  • Raw and corrected readings with depth
  • Graphs of readings and deformability parameters
  • Methods and assumptions for derived parameters
  • Deformability variation logs vs. depth or distance from collar

Summary Table: Equipment Specs

flowchart LR
    A[Test Hole] --> B[Calibration Cylinder]
    B --> C[Known Elastic Properties]
    C --> D[Calibration of Probe]
    D --> E[Pressure Measuring System]
    E --> F[Data Acquisition]
    F --> G[Test Reporting]

This ensures precise, traceable, and reliable in-situ deformability testing per IS 12955 Part 1.

IS 12955 Part 1: Test Procedure and Calibration Key Points

1. Calibration (Clause 6.1)

• Use calibration cylinders matching the test hole diameter and probe active length.
• Cylinders must have known elastic properties for accurate calibration.

2. Calibration Equipment (Clause 5.2)

• Calibration cylinders should have:
  • Internal diameter = test hole diameter
  • Length ≈ active length of the probe

3. Pressure Measuring System (Clause 5.5.2)

• Use a Bourdon gauge or electrical transducer.
• Range must cover test pressures.
• Reading sensitivity should be better than ±2% of the range.

4. Calculation of Calibration Constant (Clause 7.1)

• Calibration constant (K) relates measured pressure to strain or displacement.
• Formula (general form):

[ K = \frac{\Delta \text{Measured Output}}{\Delta \text{Applied Pressure}} ]

• Use calibration data from cylinders to find K for the specific probe.

Summary Table for Calibration Setup

flowchart LR
    A[Test Setup] --> B[Calibration Cylinder]
    B --> C[Known Elastic Properties]
    A --> D[Pressure Measuring System]
    D --> E[Bourdon Gauge / Transducer]
    E --> F[Range & Sensitivity Check]
    C & F --> G[Calculate Calibration Constant]

This ensures precise and reliable measurement during testing per IS 12955 Part 1.

IS 12955 Part 1 - Analysis of Test Data: Key Points & Formulas

Reporting Requirements (Clause 8.2)

• Tabulated Data: Raw and corrected readings with measurement depths.
• Graphs: Pressure vs. dilation plots (e.g., Fig. 3 in the code).
• Deformability Parameters: Derived values (e.g., modulus, compressibility) tabulated and graphed against applied pressure.
• Depth Logs: Variation of deformability parameters with depth or distance from drill collar.

Test Procedure (Clause 6.2.8)

• After each test, pressure is released.
• Probe is relocated for subsequent tests.

Site-wide Reporting (Clause 8.1)

• Drilling details (agency, method, equipment).
• Geotechnical logs including groundwater levels, rock types.
• Discontinuity characteristics per IS 11315.
• Calibration methods and full results.

Analysis & Calculations (Clause 7.4)

• Non-linear soil/rock behavior is considered.
• Use iterative or curve-fitting methods to derive deformability parameters from pressure-dilation data.

Typical Formula for Deformability Parameter (Modulus, E)

[ E = \frac{\Delta p}{\Delta \epsilon} ]

• ( \Delta p ) = change in applied pressure (MPa)
• ( \Delta \epsilon ) = corresponding strain or dilation (dimensionless)

Example Table Format for Reporting

graph TD
A[Start Test] --> B[Apply Pressure]
B --> C[Record Dilation]
C --> D[Calculate Modulus]
D --> E{More Depths?}
E -- Yes --> F[Relocate Probe]
F --> B
E -- No --> G[Compile Data & Graphs]

Summary:
IS 12955 Part 1

IS 12955 Part 1: Reporting of Results (Clauses 8.1, 8.2, 7.4.2)

Key Reporting Requirements

1. Site-wide Reporting (Clause 8.1)

• Drilling details: agency, method, equipment.
• Geotechnical logs: drill core, casing/cementing, groundwater, rock types, test locations.
• Discontinuities: characteristics within ±0.5 m of test sections (per IS 11315).
• Calibration: methods, equipment, deviations, full calibration results.

2. Test-specific Reporting (Clause 8.2)

• Tabulated readings: raw & corrected values with measurement depths.
• Graphs: pressure vs. deformation, deformability parameters vs. applied pressure.
• Deformability logs: variation with depth or distance from drill hole collar.

Key Formula (Clause 7.4.2)

Pressure vs. dilation curve:

[ V_m = x \times \left(n - \frac{P_1}{M_s}\right) \quad (m^3) ]

• (V_m): volume related to dilation
• (P_1): pressure
• (M_s), (n), (x): test-specific parameters

This curve is analogous to Monard pressuremeter tests.

Summary Table for Reporting Components

flowchart TD
    A[Site-wide Reporting

IS 12955 Part 1 references several related Indian Standards (IS 11315 Parts 1 to 11) for quantitative description of rock mass discontinuities:

Key Points:

• These IS codes provide standardized methods to characterize rock discontinuities crucial for geotechnical and structural design.
• Each part focuses on a specific parameter (e.g., Part 1: Orientation, Part 2: Spacing).
• Use these standards to ensure consistent data collection and analysis in rock engineering.

BIS & Standard Mark:

• BIS ensures quality through inspection, testing, and certification.
• The Standard Mark guarantees compliance and continuous quality control.

Contact & Updates:

• Indian Standards are periodically reviewed and amended.
• For latest versions or amendments, contact BIS regional offices.

flowchart LR
  A[IS 12955 Part 1] --> B[IS 11315 Part 1: Orientation]
  A --> C[IS 11315 Part 2: Spacing]
  A --> D[IS 11315 Part 3: Persistence]
  A --> E[IS 11315 Part 4: Roughness]
  A --> F[IS 11315 Part 5: Wall Strength]
  A --> G[IS 11315 Part 6: Aperture]
  A --> H[IS 11315 Part 7: Filling]
  A --> I[IS 11315 Part 8: Seepage]
  A --> J[IS 11315 Part 9: Number of Sets]
  A --> K[IS 11315 Part 10: Block Size]
  A --> L[IS 11315 Part 11: Core Recovery & Rock Quality]

For detailed procedures, refer to each IS 11315 part as per your rock mass parameter of interest.