Joint Volume Jv
Calculate Jv as reciprocal normal spacings plus random-joint frequency; conventional Jv units are m⁻¹ despite its name, with no assumed RQD conversion.
Description
Joint spacing summarizes the frequency of discontinuities in rock.
Joint spacing summarizes the frequency of discontinuities in rock. The conventional Jv index sums reciprocal normal spacings of joint sets plus a separately supplied random-joint frequency.1
The tool returns volumetricJointCountPerM. The computation uses supplied observations and parameters rather than acquiring measurements.
When to use Joint Volume Jv
Use this for the following task: Calculate Jv as reciprocal normal spacings plus random-joint frequency; conventional Jv units are m⁻¹ despite its name, with no assumed RQD conversion. Prepare observations and calibration parameters on the same unit and reporting basis.
How to use Joint Volume Jv and understand its results
- Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
- Enter jointSetNormalSpacingsM, randomJointFrequencyPerM according to the field table, then run the tool.
- Read volumetricJointCountPerM. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
- Review the supplied assumptions and calibration before comparing or reporting the result.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| jointSetNormalSpacingsM | Joint set normal spacings m | list of number | Required |
| randomJointFrequencyPerM | Random joint frequency per m | number | Required |
Provide a nonempty list of positive spacings measured normal to each joint set and a nonnegative random frequency. Return the sum in m⁻¹.
Jv = Σ(1/normalSpacingM)+randomFrequencyPerM The symbols and boundary conditions refer to the supplied fields and the implementation described above.
| Output field | Meaning | Value type |
|---|---|---|
| volumetricJointCountPerM | Volumetric joint count per m | number |
{
"input": {
"jointSetNormalSpacingsM": [
0.5,
1,
2
],
"randomJointFrequencyPerM": 0.5
},
"output": {
"volumetricJointCountPerM": 4
}
}Limitations and assumptions
Despite its name, this index has reciprocal-length units. Orientation bias, rock-quality designation and strength are not inferred from the supplied spacings.
Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.
Alternative or Complementary methods
Choose Core Recovery Percentage when you need its operation: Compute run and length-weighted total core recovery from all recovered material; distinct from RQD intact-piece length filtering. Choose Ground Support Interaction for the complementary operation: Intersect piecewise-linear supplied ground/support curves within bounds; missing, multiple and coincident equilibria are errors, not stability certifications.
Background reference: Pillar and Roof Span Design Guidelines for Underground Stone Mines.
References
-
Pillar and Roof Span Design Guidelines for Underground Stone Mines — NIOSH, Centers for Disease Control and Prevention
Similar or alternative tools
- Core Recovery Percentage
Compute run and length-weighted total core recovery from all recovered material; distinct from RQD intact-piece length filtering.
- Ground Support Interaction
Intersect piecewise-linear supplied ground/support curves within bounds; missing, multiple and coincident equilibria are errors, not stability certifications.