Rock Bolt Length

Convert normal loosened-zone depth to bolt path and add caller anchorage/exposed allowances; no anchorage strength or support certification.

Description

An inclined bolt travels farther through a loosened zone than a bolt normal to that zone.

An inclined bolt travels farther through a loosened zone than a bolt normal to that zone. Additional anchorage and exposed allowance are separate axial lengths.

The tool returns lengthThroughLoosenedZoneM (length through loosened zone m); totalBoltLengthM (total bolt length m). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.

When to use Rock Bolt Length

Use Rock Bolt Length when you already have loosenedZoneDepthNormalM, boltAngleFromNormalDegrees, anchorageBeyondZoneM, exposedAllowanceM and want lengthThroughLoosenedZoneM, totalBoltLengthM. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.

How to use Rock Bolt Length and understand its results

Enter loosenedZoneDepthNormalM, boltAngleFromNormalDegrees, anchorageBeyondZoneM, exposedAllowanceM using the field table below. Match the units, ordering and data boundaries described in the calculation.
Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
Read lengthThroughLoosenedZoneM, totalBoltLengthM. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.

Input field	Meaning	Value type and bounds	Requirement
loosenedZoneDepthNormalM	Loosened zone depth normal m	number	Required
boltAngleFromNormalDegrees	Bolt angle from normal degrees	number	Required
anchorageBeyondZoneM	Anchorage beyond zone m	number	Required
exposedAllowanceM	Exposed allowance m	number	Required

Use nonnegative normal depth and allowance, positive anchorage and angle in [0,90) degrees.

zoneLength = normalDepth/cos(angleFromNormal); total = zoneLength+anchorage+allowance

The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.

json

{
  "input": {
    "loosenedZoneDepthNormalM": 2,
    "boltAngleFromNormalDegrees": 60,
    "anchorageBeyondZoneM": 1,
    "exposedAllowanceM": 0.2
  },
  "output": {
    "lengthThroughLoosenedZoneM": 3.999999999999999,
    "totalBoltLengthM": 5.199999999999999
  }
}

Limitations and assumptions

The loosened boundary is assumed planar. Anchorage adequacy, capacity and ground stability are not assessed.

Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.

Alternative or Complementary methods

Rock Bolt Spacing: Calculate square-grid tributary-load bolt-spacing screen; anchorage, wedges, corrosion and dynamics are not modeled or certified. Shotcrete Volume: Estimate placed and batch volumes with rebound as a fraction of delivered batch; support adequacy is external.

Methodological background: Pillar and Roof Span Design Guidelines for Underground Stone Mines.^[1]

References

Pillar and Roof Span Design Guidelines for Underground Stone Mines — NIOSH, Centers for Disease Control and Prevention

Similar or alternative tools

Rock Bolt Spacing
Calculate square-grid tributary-load bolt-spacing screen; anchorage, wedges, corrosion and dynamics are not modeled or certified.
Shotcrete Volume
Estimate placed and batch volumes with rebound as a fraction of delivered batch; support adequacy is external.