Rock Quality Designation Calculator

How It Works

1. Enter Core-Run Length

   Input the drilled core-run length in the selected unit system. The run length remains the denominator even when recovery is low.

2. Enter Logged Piece Lengths

   Enter sound, intact core pieces measured along the centerline after documented mechanical drilling breaks have been reconciled.

3. Screen Measured or Theoretical RQD

   Measured mode sums pieces at least 100 mm (4 in). Theoretical mode uses the Priest-Hudson relationship with lambda entered as discontinuities per meter.

4. Review Warnings and Source Gaps

   Use the quality band, recovery, RMR component, and warnings as a logging screen only, then verify against current project procedure and geotechnical review.

Built For

• Core logging review where measured RQD arithmetic needs a transparent source boundary
• Checking whether low recovery, core loss, or break-call uncertainty should be escalated in the boring log
• Screening the RQD component before a full RMR or Q-system workflow handled by qualified personnel
• Comparing measured RQD with a Priest-Hudson theoretical value from documented discontinuity frequency
• Preparing QA notes that separate arithmetic, assumptions, source pointers, and residual review gaps
• Teaching RQD threshold, recovery, and classification concepts without claiming design approval

Features & Capabilities

Measured RQD Screen

Sums sound core pieces at least 100 mm (4 in) and divides by the total core-run length, with capped display percentages and raw overrun warnings.

Core Recovery Check

Shows total recovered length versus run length so low-recovery intervals do not hide behind the RQD numerator.

Source-Aware Classification

Maps RQD percentage to Very Poor, Poor, Fair, Good, or Excellent while warning that RQD alone is not a rock-mass design result.

RMR RQD Component

Shows the RMR RQD-component band values of 3, 8, 13, 17, or 20 without presenting a full RMR classification.

Theoretical RQD Mode

Uses the Priest-Hudson relationship for lambda in discontinuities per meter and surfaces the model assumptions.

Report and PDF Export

Exports inputs, outputs, assumptions, source warnings, and source pointers for review packets, not sealed design documents.

Assumptions

• Entered piece lengths are sound, intact core measured along the core centerline.
• Mechanical drilling and handling breaks have been fitted together or documented before entry.
• Pieces must be 100 mm (4 in) or longer to count toward the measured RQD numerator.
• Theoretical mode lambda is a documented linear discontinuity frequency in fractures per meter.

Limitations

• RQD is direction-dependent; one borehole or core run may not capture all fracture sets.
• Soft, altered, weathered, or damaged core may produce low or misleading RQD values.
• RQD does not capture joint condition, aperture, infilling, groundwater, strength, or orientation effects.
• Theoretical RQD assumes a spacing model and can be biased by scanline method and anisotropy.
• This page is not the current ASTM standard text or a project logging procedure.

References

• ASTM D6032/D6032M-17 - Standard Test Method for Determining Rock Quality Designation (RQD) of Rock Core.
• FHWA NHI-06-088 - Soils and Foundations, Volume I, core recovery and RQD logging discussion.
• USACE EM 1110-1-2908 - Rock Foundations, RQD definition and classification bands.
• USACE ETL 1110-2-581 - Rock Mass Characterization for Dam Foundations, theoretical RQD relationship and limits.

Frequently Asked Questions