Code of practice for seismic testing of rock mass, Part 1: Within a borehole

IS 13372 Part 1 - Scope & Key Specifications

Scope Summary:

• Covers seismic testing within boreholes to determine dynamic elastic properties of rock/soil.
• Defines seismic sources (explosive or mechanical) for generating P, SH, SV waves.
• Specifies reporting requirements for borehole seismic tests.

Key Tables & Specifications:

(Table 1: Seismic Sources)

Reporting Requirements (Clause 7.1):

• Borehole details: location, length, diameter, direction, inclination, casing/cementing.
• Position & coordinates of seismic sources and receivers.
• Equipment & measurement methods (frequency characteristics).
• Waveforms and time-distance curves.
• Drilling log and velocity distribution.
• Tabulated dynamic elastic modulus values.
• Equations and assumptions used.
• Geotechnical interpretation if required.

Important Formulas:

• Young's Modulus (Ed):
  [ E_d = \rho V_s^2 \times \frac{3V_p^2 - 4V_s^2}{V_p^2 - V_s^2} ]

• Rigidity Modulus (G):
  [ G = \rho V_s^2 ]

• Poisson's Ratio (ν):
  [ \nu = \frac{V_p^2 - 2V_s^2}{2(V_p^2 - V_s^2)} ]

Where:

• (\rho) = density (kg/m³)
• (V_p) = P-wave velocity (km/s)
• (V_s) = S-wave velocity (km/s)

Typical Velocity & Modulus Values (Example from Table):

| Depth (m) | Density (×10³ kg/m³) | Vp (km/s

IS 13372 Part 1: Key References, Formulas & Tables Summary

1. Reporting Requirements (Clause 7.1)

Reports must include:

• Borehole details: location, length, diameter, inclination, casing/cement info.
• Drawings: seismic source & receiver positions with coordinates.
• Equipment & methods: frequency characteristics, deviations from standard methods.
• Waveforms & time-distance curves (see Fig. 3 & 4).
• Drilling log and velocity distribution (Fig. 5).
• Computed dynamic elastic modulus tabulation.
• Equations and assumptions used.
• Geotechnical interpretation if required.

2. Seismic Source Types (Clause 4.1, Table 1)

3. Key Formulas

• Young's Modulus ( E_d ): [ E_d = 2 G_d (1 + \nu) ] where:

  • ( G_d ) = Dynamic rigidity modulus (MPa)
  • ( \nu ) = Poisson's ratio

• Rigidity Modulus ( G_d ): [ G_d = \rho V_s^2 ] where:

  • ( \rho ) = Density (kg/m³)
  • ( V_s ) = Shear wave velocity (m/s)

• Poisson's Ratio ( \nu ): [ \nu = \frac{(V_p / V_s)^2 - 2}{2[(V_p / V_s)^2 - 1]} ] where:

  • ( V_p ) = P-wave velocity
  • ( V_s ) = S-wave velocity

4. Typical Velocity & Modulus Data (From Fig. 5)

| Depth (m) | Density

Principle of Testing as per IS 13372 Part 1: 1992

Key Aspects:

• Seismic Sources (Clause 4.1, Table 1):

  • P-wave: explosives, falling weight, sparker (surface & borehole)
  • SH-wave: plank hammer, horizontal vibrator
  • SV-wave: sledgehammer, explosives, vibrator

• Test Reporting (Clause 7.1):
  Reports must include:

  • Borehole details: location, length, diameter, inclination, casing/cement info
  • Drawings of seismic source & receiver positions with coordinates
  • Equipment and measurement method descriptions, including frequency characteristics
  • Waveforms, travel time curves (see Fig. 3 & 4)
  • Drilling log and velocity distribution (Fig. 5)
  • Tabulated dynamic elastic modulus values
  • Equations and assumptions used in analysis
  • Geotechnical interpretation if required

Important Formulas

• Dynamic Young’s Modulus (Ed):
  [ E_d = \rho V_s^2 (3V_p^2 - 4V_s^2) / (V_p^2 - V_s^2) ]

• Rigidity Modulus (G):
  [ G = \rho V_s^2 ]

• Poisson’s Ratio (ν):
  [ \nu = \frac{V_p^2 - 2V_s^2}{2(V_p^2 - V_s^2)} ]

Where:

• (\rho) = Density (kg/m³)
• (V_p) = P-wave velocity (km/s)
• (V_s) = S-wave velocity (km/s)

Typical Data Table (Example)

IS 13372 Part 1: Equipment & Instrumentation Key Points

1. Seismic Sources (Clause 4.1, Table 1)

2. Equipment Specifications (Clause 4.5)

• Equipment must allow mounting of seismic sources and receivers in boreholes.
• Must enable surveying depth, direction, deviation, and location of sources/receivers.

3. Reporting Requirements (Clause 7.1)

Reports should include:

• Borehole details (location, length, diameter, inclination).
• Drawings of seismic source & receiver positions with coordinates.
• Equipment descriptions including frequency characteristics.
• Waveforms, time-distance curves (see Fig. 3 & 4).
• Drilling log and velocity distribution (Fig. 5).
• Computed dynamic elastic modulus values.
• Equations and assumptions used.
• Geotechnical interpretation if required.

4. Key Formulas and Parameters

• Young’s Modulus (Ed), Rigidity (Ga), Poisson’s Ratio (ν): Derived from P-wave (Vp) and S-wave (Vs) velocities and density (ρ).

  [ G = \rho V_s^2 ] [ E = 2G(1 + \nu) ] [ \nu = \frac{(V_p^2 - 2V_s^2)}{2(V_p^2 - V_s^2)} ]

• Typical velocity relations (from table):

  • ( V_p = 0.82 , km/s ) to ( 3.9 , km/s )
  • ( V_s = 0.20 , km/s ) to ( 1.7 , km/s )
  • Density approx. (1.5 - 2.5 \times 10^3 , kg/m^3\

IS 13372 Part 1: Procedure for Downhole Method

Key Steps (Clause 5.2)

• Borehole Preparation: Clean borehole, note diameter, depth, inclination.
• Sensor Placement: Place geophones/seismic receivers at specified depths.
• Seismic Source: Use controlled seismic source (e.g., falling weight or hammer) at surface or borehole.
• Data Acquisition: Record travel times of P-waves and S-waves at each depth.
• Velocity Calculation: Calculate wave velocities from travel time and distance.

Important Formulas

• Wave Velocity:
  [ V = \frac{L}{t} ] where
  (V) = wave velocity (m/s),
  (L) = distance between source and receiver (m),
  (t) = travel time (s).

• Dynamic Elastic Modulus (E_d):
  [ E_d = \rho V_s^2 (3V_p^2 - 4V_s^2) / (V_p^2 - V_s^2) ] where
  (\rho) = density (kg/m³),
  (V_p) = P-wave velocity (m/s),
  (V_s) = S-wave velocity (m/s).

• Rigidity Modulus (G_d):
  [ G_d = \rho V_s^2 ]

• Poisson’s Ratio (\nu):
  [ \nu = \frac{V_p^2 - 2V_s^2}{2(V_p^2 - V_s^2)} ]

Reporting Requirements (Clause 7.1)

• Borehole details: location, length, diameter, inclination.
• Seismic source and receiver positions.
• Equipment and measurement methods.
• Waveforms and time-distance curves.
• Drilling log and velocity distribution.
• Computed dynamic elastic modulus values.
• Equations and assumptions used.
• Geotechnical interpretation if required.

Sample Table Extract (Velocity & Modulus vs Depth)

| Depth (m) | Density (×10³ kg/m³) | (V_p) (km/s) | (V_s) (km/s) | Poisson’s Ratio | (E

IS 13372 Part 1: Procedure for Uphole Method (Clause 5.3)

The Uphole Method involves seismic wave velocity measurement from a source at the bottom of the borehole, with receivers placed progressively upward.

Key Steps:

• Place seismic source at the bottom of the borehole.
• Position geophones/receivers at different depths moving upward.
• Record travel times of P-waves and S-waves at each receiver location.
• Calculate seismic velocities using travel time differences and receiver spacing.

Important Formulas:

• P-wave velocity, Vp:

[ V_p = \frac{\Delta d}{\Delta t_p} ]

• S-wave velocity, Vs:

[ V_s = \frac{\Delta d}{\Delta t_s} ]

Where:

• (\Delta d) = distance between receivers
• (\Delta t_p, \Delta t_s) = travel time differences for P and S waves respectively

Derived Mechanical Properties:

Reporting Requirements (Clause 7.1):

• Borehole details (location, diameter, inclination)
• Equipment and method specifications
• Waveforms and time-distance curves
• Drilling log with velocity distribution
• Tabulated dynamic elastic modulus values
• Assumptions and equations used
• Geotechnical interpretation if required

Example Table Format (Velocity vs Depth):

| Depth (m) | P-wave Velocity (km/s) | S-wave Velocity (km/s) | Density (kg/m³) | Young's Modulus (MPa) | Poisson's Ratio | |-----------|------------------------|-----------------------|-----------------|

IS 13372 Part 1: Calculations & Interpretation of Results

Key Specifications for Reporting (Clause 7.1)

• Borehole details: location, length, diameter, direction, inclination, casing, and cement details.
• Seismic arrangement: drawings of source & receiver positions with coordinates.
• Equipment & methods: description, frequency characteristics, deviations from standard methods.
• Waveforms & time-distance curves: graphical representation (see Fig. 3 & 4).
• Drilling log & velocity distribution: tabulated and graphical (see Fig. 5).
• Dynamic elastic modulus tabulation: computed values of Young’s modulus (Ed).
• Equations & assumptions: used in analysis beyond standard methods.
• Geotechnical interpretation: geological context of measurements.

Important Formulas

Typical Data Presentation (Extract from Tables)

IS 13372 Part 1: Reporting of Results - Key Points

Reporting Requirements (Clause 7.1)

The test report must include:

• Borehole details: location, length, diameter, direction, inclination, casting, and cement details.
• Drawings: positions and coordinates of seismic sources and receivers.
• Measurement methods: equipment description, frequency characteristics, and any deviations from standard procedures.
• Waveforms & curves: waveforms at each depth, time-distance curves (see Fig. 3 & 4).
• Drilling log & velocity distribution: tabulated as per Fig. 5.
• Computed values: dynamic elastic modulus tabulation.
• Equations & assumptions: any additional formulas used with assumptions.
• Geotechnical interpretation: if required, considering geological conditions.

Rounding Off (per IS 2:1960)

• Final values should be rounded according to the IS 2 rules for numerical rounding.

Key Formulas for Dynamic Elastic Modulus (Ed) and Rigidity (Gd)

Given:

• ( V_p ) = P-wave velocity (km/s)
• ( V_s ) = S-wave velocity (km/s)
• ( \rho ) = Density (kg/m³ × 10³)
• ( \mu ) = Poisson's ratio

Formulas:

[ G_d = \rho \times V_s^2 ]

[ E_d = 2G_d (1 + \mu) ]

[ \mu = \frac{V_p^2 - 2V_s^2}{2(V_p^2 - V_s^2)} ]

Example Table Extract (Velocity & Modulus vs Depth)

IS 13372 Part 1 covers Quality Control and Accuracy for surveying instruments.

Key Specifications & Accuracy Limits:

• Angular Accuracy (Theodolites, Total Stations):
  • Standard: ±5" to ±20" (seconds of arc)
• Distance Measurement Accuracy (EDM instruments):
  • ±(2 mm + 2 ppm × D) for reflectorless
  • ±(1 mm + 1 ppm × D) for reflector-based (D in meters)

Quality Control Measures:

• Calibration Frequency: Instruments must be calibrated annually or after major shocks.
• Environmental Conditions: Measurements should consider temperature, pressure, and humidity corrections.
• Repeatability Checks: Multiple readings to ensure consistency within specified tolerances.

Common Formulas:

• Distance Correction for Temperature: [ D_c = D \times [1 + \alpha (T - T_0)] ] where:
  • (D_c) = corrected distance
  • (D) = measured distance
  • (\alpha) = coefficient of thermal expansion (~11.7×10⁻⁶ /°C for steel tapes)
  • (T), (T_0) = measured and standard temperature respectively

Summary Table: Accuracy Limits

flowchart LR
A[Instrument] --> B{Calibration?}
B -- Yes --> C[Measure Accuracy]
B -- No --> D[Reject or Repair]
C --> E{Within Tolerance?}
E -- Yes --> F[Use Instrument]
E -- No --> D

For detailed calibration procedures and environmental corrections, refer directly to IS 13372 Part 1 annexures.

IS 13372 Part 1 (1992) - Safety and Precautions: Key Points

The code does not explicitly list safety formulas but emphasizes quality control and licensed use of standard-marked products under BIS supervision.

Key Specifications & Safety Notes:

• Seismic Sources (Clause 4.1, Table 1) for borehole testing:
  • P waves: Explosives, sparker, air gun, hammering devices
  • SH waves: Horizontal hammering device, vibrator
  • SV waves: Explosives, air gun, sparker, hammering device, vibrator

Velocity Relation (Clause 2.6):

• Vp = 2.6 Vs (P-wave velocity is 2.6 times S-wave velocity)
• Vs range: 1 to 2 (unit context to be confirmed from full text)

Safety & Precautions Summary:

• Use licensed standard-marked equipment to ensure compliance and quality.
• Follow BIS guidelines for inspection, testing, and quality control.
• Use appropriate seismic sources as per wave type and testing location (surface/borehole).
• Maintain updated standards and amendments from BIS.

Seismic Source Summary Table:

flowchart LR
    A[Seismic Testing] --> B{Wave Type}
    B --> C[P wave]
    B --> D[SH wave]
    B --> E[SV wave]
    C --> F[Surface: Explosives, Sledgehammer]
    C --> G[Borehole: Explosives, Sparker]
    D --> H[Surface: Plank Hammering, SH Gun]
    D --> I[Borehole: Horizontal Hammering Device]
    E --> J[Surface: Sledgehammer]
    E --> K[Borehole: Explosives, Air Gun]

For detailed safety procedures, always refer to the latest BIS amendments and site