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IS 10782:1983 is the Indian Standard (BIS) for method for laboratory determination of dynamic modulus of rock core specimens. This standard outlines the laboratory procedure for determining the dynamic elastic properties of rock core specimens, such as Young's modulus, shear modulus, and Poisson's ratio. The method is based on measuring the transit time of high-frequency ultrasonic pulses through a prepared cylindrical sample.
Method for laboratory determination of dynamic modulus of rock core specimens
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Meticulous specimen preparation is paramount; ends must be perfectly flat, parallel, and perpendicular to the core axis to ensure accurate velocity measurements.
! A good acoustic coupling agent (e.g., grease, petroleum jelly) is essential between the transducers and the rock specimen to ensure efficient energy transmission.
! The determined modulus represents the property of the intact rock core and does not reflect the influence of discontinuities (joints, fractures) present in the in-situ rock mass.
Standard Test Method for Laboratory Determination of Pulse Velocities and Ultrasonic Elastic Constants of Rock
Both standards determine dynamic elastic moduli of rock cores by measuring compressional and shear wave velocities.
ISRM Suggested Method (1978)International Society for Rock Mechanics (ISRM), International
HighCurrent
Suggested Method for Determining Sound Velocity
Provides the foundational international methodology for measuring ultrasonic wave velocities to calculate dynamic properties.
BS EN 14579:2004British Standards Institution / European Committee for Standardization, UK/EU
MediumCurrent
Natural stone test methods - Determination of sound speed propagation
Focuses specifically on sound speed in natural stone (for dimension stone), which is a subset of the broader rock mechanics scope of IS 10782.
Key Differences
≠IS 10782 recommends a specimen length-to-diameter (L/D) ratio of 2.0 to 2.5, whereas ASTM D2845 suggests a minimum of 2:1 but prefers 5:1 to minimize near-field and end-effect errors.
≠ASTM D2845 provides more specific guidance on transducer frequency (typically 500 kHz to 1 MHz) and discusses the relationship between wavelength and specimen/grain size, which is only mentioned as 'suitable high frequency' in IS 10782.
≠International standards like ASTM D2845 often mandate more detailed reporting, including sample saturation condition, temperature, specific coupling agent used, and a statement on precision and bias, which are less emphasized in IS 10782.
≠The procedure for system 'zero time' calibration is more explicitly detailed in ASTM D2845, often requiring calibration with standard reference bars of known velocity, whereas it is mentioned more generally in IS 10782.
Key Similarities
≈All standards are based on the same fundamental principle: using the ultrasonic pulse velocity (UPV) method to measure the transit time of compressional (P-wave) and shear (S-wave) waves through a prepared rock core.
≈The core set of required apparatus is functionally identical across all standards, comprising a pulse generator, transmitting/receiving transducers, and a high-resolution timing device (e.g., oscilloscope).
≈The mathematical formulas used to calculate dynamic Young's Modulus, Shear Modulus, and Poisson's ratio from the measured wave velocities (Vp, Vs) and bulk density (ρ) are identical.
≈All standards require careful preparation of the specimen, emphasizing that the ends must be flat, parallel, and perpendicular to the core's longitudinal axis to ensure good transducer contact and accurate length measurement.
Parameter Comparison
Parameter
IS Value
International
Source
Specimen L/D Ratio
2.0 to 2.5
Minimum 2:1, preferably 5:1
ASTM D2845-19
Specimen End Flatness
Not quantitatively specified (implied 'flat')
Flat to within 0.02 mm
ASTM D2845-19
End Perpendicularity to Axis
Ends shall be at right angles to the longitudinal axis
Shall not depart from perpendicularity by more than 0.25°
ASTM D2845-19
Recommended Transducer Frequency
Suitable high frequency transducers
Typically 500 kHz to 1 MHz
ASTM D2845-19
Formula for Shear Modulus (Gd)
Gd = ρ * Vs²
G = ρ * Vs²
ASTM D2845-19
Formula for Poisson's Ratio (νd)
νd = [0.5(Vp/Vs)² - 1] / [(Vp/Vs)² - 1]
ν = [0.5(Vp/Vs)² - 1] / [(Vp/Vs)² - 1]
ASTM D2845-19
Primary Outputs
Dynamic Young's modulus, modulus of rigidity, and Poisson's ratio
Compressional and shear wave velocities, and the dynamic elastic constants
ASTM D2845-19
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Specimen Length to Diameter (L/D) Ratio2.0 to 2.5
Minimum Specimen Diameter45 mm (preferably NX size 54.7 mm)
Specimen End Flatness Tolerance0.02 mm
Specimen End Perpendicularity to Axiswithin 0.001 radian (approx 0.06 degrees)
To specify the laboratory method for determining the dynamic modulus of elasticity of intact rock core specimens using ultrasonic pulse velocity.
What is the required L/D ratio for the rock specimen?+
The length-to-diameter ratio (L/D) of the specimen must be between 2.0 and 2.5 (Clause 4.1).
How is the dynamic Young's modulus calculated?+
It is calculated based on the rock's bulk density (ρ), the compressional wave velocity (Vp), and the dynamic Poisson's ratio (νd) using the formula in Clause 6.1.1.
Does this test give the static or dynamic modulus?+
This test determines the dynamic modulus, which is typically higher than the static modulus obtained from a compression test.