Method of test for laboratory determination of resistivity on rock specimen

IS 14436 - Scope & Key Specifications

Scope (Clause 1.2)

• Testing can be performed in laboratory or at site.
• Related standards referenced:
  • IS 9179:1979 – Preparation of rock specimens for lab testing.
  • IS 13030:1991 – Lab determination of water content, porosity, density, and related rock properties.

Key Data Recording (Clause 6.2)

• Record number, length, and area of samples on data sheet (Annex A).

Apparatus Specifications (Clause 1.96)

This standard ensures reliable electrical testing of rock samples with high input impedance and noise rejection, suitable for both lab and field environments.

IS 14436 - Definitions & Key Specifications

1. Definitions (Clause 3.0)

• The standard defines terms related to rock specimen testing, resistivity measurement, and sample preparation.
• These definitions ensure uniform understanding for testing procedures.

2. Sample Details (Clause 6.2)

• Record number, length, and cross-sectional area of each rock specimen in the data sheet (Annex A).
• Accurate specimen dimensions are critical for resistivity calculation.

3. Resistivity Calculation (Clause 9.2)

• Resistivity (ρ) for each specimen is calculated using the formula in Clause 8.1 (not fully provided here).
• Results are expressed to two significant figures.
• Average resistivity is computed for the sample set.

4. Testing Locations (Clause 1.2)

• Tests can be conducted in the laboratory or on-site.

5. Referenced Standards

Common Resistivity Formula (from typical rock resistivity tests):

[ \rho = R \times \frac{A}{L} ] Where:

• ( \rho ) = Resistivity (Ω·m)
• ( R ) = Measured resistance (Ω)
• ( A ) = Cross-sectional area of specimen (m²)
• ( L ) = Length of specimen (m)

flowchart LR
    A[Rock Specimen] --> B[Measure Length (L)]
    A --> C[Measure Cross-sectional Area (A)]
    A --> D[Measure Resistance (R)]
    B & C & D --> E[Calculate Resistivity: ρ = R * (A / L)]
    E --> F[Record in Data Sheet (Annex A)]
    F --> G[Compute Average Resistivity]

This summary aligns with IS 14436 clauses and common engineering practice for resistivity testing of rock specimens.

IS 14436: Key Formulas & Specifications for Principle (Clause 9.2, 6.2, 1.96)

Principle:
Measurement of resistivity of concrete specimens using electrical methods.

1. Resistivity Calculation (Clause 9.2)

The resistivity (\rho) (in ohm-cm) is calculated as:

[ \rho = R \times \frac{A}{L} ]

• R = measured resistance (ohms) from the specimen
• A = cross-sectional area of the specimen (cm²)
• L = length of the specimen (cm)

Calculate resistivity for each specimen and report to two significant figures along with the average.

2. Sample Data (Clause 6.2)

Record the following in the data sheet (Annex A):

• Number of specimens
• Length of each specimen (L)
• Cross-sectional area (A)

3. Instrument Specifications (Clause 1.96)

Summary Diagram: Resistivity Measurement Setup

flowchart LR
    A[Apply Voltage] --> B[Measure Current]
    B --> C[Calculate Resistance (R)]
    C --> D[Use formula ρ = R * (A/L)]
    D --> E[Obtain Resistivity (ρ)]

Note: Use precise specimen dimensions and calibrated instruments for accurate resistivity measurement as per IS 14436.

IS 14436: Preparation of Samples - Key Points

1. Sample Selection & Preparation (Clause 4.1)

• Samples must represent the average rock type.
• Preparation follows IS 9179:1979 (Method for preparation of rock specimens).
• Protect samples from frost and extreme heat during sampling and transport.

2. Sample Data Recording (Clause 6.2)

• Record number, length (L), and cross-sectional area (A) of samples in the data sheet (Annex A).

3. Resistivity Formula (Clause 3.4)

[ \rho = R \times \frac{A}{L} ]

Where:

• (\rho) = Resistivity (ohm·m)
• (R) = Resistance (ohms)
• (A) = Cross-sectional area (m²)
• (L) = Length of sample (m)

4. Related Standards for Reference

Summary Diagram: Sample Preparation Flow

flowchart TD
    A[Select representative rock sample] --> B[Prepare specimen as per IS 9179]
    B --> C[Protect sample from frost/extreme heat]
    C --> D[Measure & record length (L) and area (A)]
    D --> E[Conduct tests (e.g., resistivity using R, L, A)]

Ensure adherence to IS 9179 for specimen preparation and record all sample dimensions accurately for valid test results.

IS 14436: Apparatus Key Specifications & Formulas

• Cycle Time: ≤ 1.96 seconds (Clause 1.96)
• Input Impedance: 10¹² ohms
• 50-60 Hz Rejection: 60 dB
• Primary Voltage Range: 40 mV to 10 V (selectable in 6 steps)
• Resolution: 0.4 mV
• Accuracy: ±1.5% of full scale
• Polarity Indication: Automatic
• Weight: Approx. 6 kg
• Power Supply: Rechargeable battery packs

Operational Guidelines (Clause 5.5 & 5.6)

• Prefer apparatus with automatic data acquisition and computing for easier interpretation.
• Must be supplied with a detailed operation and maintenance manual.

Data Recording (Clause 6.2)

• Record number, length, and area of samples in the data sheet (Annex A).

Summary Table

flowchart TD
    A[Start Test] --> B[Set Voltage Range (40mV-10V)]
    B --> C[Check Polarity (Automatic)]
    C --> D[Acquire Data (Cycle ≤1.96s)]
    D --> E[Data Processing & Interpretation]
    E --> F[Record Sample Details (No., Length, Area)]
    F --> G[End Test & Maintenance]

This encapsulates the apparatus specifications and operational essentials per IS 14436.

IS 14436: Testing Procedure – Key Points

1. Test Location & Setup

• Tests can be performed in the laboratory or on-site (Clause 1.2).
• Site should have minimal electromagnetic interference (50/60 Hz mains disturbance) (Clause 5.8).

2. Sample Details (Clause 6.2)

• Record number, length, and cross-sectional area of each sample on the data sheet (Annex A).

3. Equipment Calibration (Clause 6.10.2)

• Calibrate equipment with a standard resistance Test Box before testing.

4. Reference Standards

• Preparation of rock specimens: IS 9179:1979
• Determination of water content, porosity, density: IS 13030:1991

Typical Data Sheet Fields (Annex A)

Calibration Check Formula

For resistance ( R ):

[ R_{\text{measured}} \approx R_{\text{standard}} \pm \text{tolerance} ]

Ensure the measured resistance matches the Test Box standard within acceptable limits.

flowchart TD
    A[Test Setup] --> B[Sample Preparation]
    B --> C[Record Sample Data]
    C --> D[Equipment Calibration]
    D --> E[Conduct Test]
    E --> F[Analyze Results]

Summary: Follow strict sample documentation, calibrate equipment with standard resistance, and minimize electromagnetic noise for reliable test results per IS 14436.

IS 14436 - Factors Affecting Test Results: Key Points

1. Factors Affecting Resistivity Test Results (Clause 7.2)

• Sample holder: Must ensure stable contact and no leakage.
• Sample preparation routine: Follow IS 9179:1979 for specimen prep.
• Sample measurement & reproducibility: Consistent dimensions and repeated tests.
• Degree of electrolyte saturation: Controls conductivity; maintain uniform saturation.
• Electrolyte composition: Varies resistivity; use standard electrolyte or note composition.
• Porosity of rock sample: Higher porosity generally lowers resistivity.

2. Sample Details (Clause 6.2)

• Record number, length, and cross-sectional area of samples on data sheet (Annex A).

3. Calibration (Clause 6.10.2)

• Use a standard resistance test box for equipment calibration before testing.

4. Reference Standards

Typical Resistivity Calculation Formula:

[ \rho = R \times \frac{A}{L} ]

Where:

• (\rho) = Resistivity (Ω·m)
• (R) = Measured resistance (Ω)
• (A) = Cross-sectional area of sample (m²)
• (L) = Length of sample (m)

Diagram: Test Setup Overview

graph LR
A[Current Electrode] --> B[Sample Holder]
B --> C[Rock Sample]
C --> D[Platinum Pick-up Electrodes]
D --> E[Receiver & Measurement Unit]
E --> F[Calibration with Standard Resistance Box]

Summary: Control sample prep, saturation, and calibration to ensure reliable resistivity measurements per IS 14436.

IS 14436: Calculation of Resistivity

Key Formula (Clause 8.1 & 3.4)

[ \boxed{ \rho = \frac{V}{I} \times \frac{A}{L} } ]

Where:

• (\rho) = Resistivity (ohm-metre)
• (V) = Voltage across specimen (mV)
• (I) = Current through specimen (mA)
• (A) = Mean cross-sectional area of specimen (m²)
• (L) = Length of specimen (m)

Alternatively, using resistance (R = \frac{V}{I}):

[ \rho = R \times \frac{A}{L} ]

Important Notes:

• Area (A) must be accurately measured (usually average of multiple cross-sections).
• Length (L) is the overall length between electrodes.
• Report resistivity to two significant figures per Clause 9.2.
• Average resistivity from multiple specimens should be reported.

Summary Table for Resistivity Calculation

flowchart TD
    A[Measure Voltage (V)] --> C[Calculate Resistance R = V/I]
    B[Measure Current (I)] --> C
    D[Measure Cross-sectional Area (A)] --> E[Calculate Resistivity ρ = R * (A/L)]
    F[Measure Length (L)] --> E
    C --> E

This formula and procedure ensure consistent laboratory determination of rock resistivity as per IS 14436.

IS 14436: Reporting of Test Results — Key Points

Clause 9.1: Test Report Must Include

• Lithologic description of rock.
• Sample orientation relative to specimen anisotropy.
• Sample source: depth, geographic location, sampling method, environment.
• Number of specimens tested.
• Specimen dimensions: diameter & length.
• Water content & degree of saturation (per IS 13030).
• Test duration.
• Date of testing & equipment used.
• Additional observations or physical data.

Clause 6.2: Data Sheet Requirements

• Record number, length, and area of samples (refer Annex A).

Clause 8.1: Resistivity Calculation Formula

[ \rho = \frac{V}{I} \times \frac{A}{L} ]

Where:

• (\rho) = Resistivity (ohm-m)
• (V) = Voltage (mV)
• (I) = Current (mA)
• (A) = Cross-sectional area (m²)
• (L) = Length of sample (m)

References:

• IS 9179:1979 — Rock specimen preparation
• IS 13030:1991 — Water content, porosity, density tests

flowchart TD
    A[Test Sample] --> B[Measure Dimensions]
    B --> C[Determine Water Content (IS 13030)]
    C --> D[Conduct Resistivity Test]
    D --> E[Calculate Resistivity \(\rho = \frac{V}{I} \times \frac{A}{L}\)]
    E --> F[Compile Test Report]
    F --> G[Include Lithology, Orientation, Source, Observations]

This ensures comprehensive, standardized reporting as per IS 14436.

IS 14436: Data Sheet for Laboratory Determination of Resistivity

Key Formula (Clause 8.1)

[ \boxed{ \rho = \frac{V}{I} \times \frac{A}{L} } ]

Where:

• (\rho) = Resistivity (ohm-metre)
• (V) = Voltage across specimen (mV)
• (I) = Current through specimen (mA)
• (A) = Mean cross-sectional area of specimen (m²)
• (L) = Length of specimen (m)

Specifications & Guidelines

• Specimen dimensions: Measure length (L) and cross-sectional area (A) accurately.
• Current & Voltage: Use calibrated equipment; current (I) in mA and voltage (V) in mV.
• Reporting: Resistivity for each specimen rounded to two significant places; also report average resistivity.
• Calibration: Use a standard resistance test box for equipment calibration (Clause 5.7).
• Precautions: Follow Clause 6.10 for test setup and measurement accuracy.

Summary Table for Reporting Resistivity

Notes:

• Resistivity values help classify rock types and assess engineering parameters.
• Laboratory resistivity supports but does not replace field resistivity tests.
• Round off results per IS 2:1960 rules.

flowchart LR
    A[Measure Specimen Dimensions] --> B[Apply Current (I)]
    B --> C[Measure Voltage (V)]
    C --> D[Calculate Resistivity \(\rho = \frac{V}{I} \times \frac{A}{L}\)]
    D --> E[Report Individual & Average Resistivity]

This concise data sheet follows IS 14436 guidelines for reliable laboratory determination

IS 14436: Technical Committee Overview & Key Specifications

Technical Committee (Annex B - Foreword)
The Rock Mechanics Sectional Committee (CED 48) comprises experts from universities, government research institutes, power boards, and industry, ensuring comprehensive standard development.

Key Details:

• Committee Members:

  • Dr. Bhawani Singh (University of Roorkee) - Convener
  • Dr. P.K. Jain, Dr. M.N. Viladkar (Alternate), Dr. R.L. Chauhan, Shri Dadeswar Gangadhar Dhayagude, and others from diverse organizations like CSIR, GSI, NTPC, IIT, and BIS.

• Roles:

  • Members represent academic institutions, government research bodies, power and irrigation departments, and private sector.
  • BIS Director General (Ex-officio Member) included.

Relevant Tables & Formats:

Annex A: Laboratory Data Sheet for Resistivity Testing

Key Formula: Resistivity Calculation

[ \rho = R \times \frac{A}{L} ]

Where:

• (\rho) = Resistivity (ohm-m)
• (R = \frac{V}{I}) = Resistance (ohms), (V) = voltage (volts), (I) = current (amperes)
• (A) = cross-sectional area (m²)
• (L) = length of the sample (m)

Rock Resistivity Range (Fig. 2 Summary)