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D6032 – Standard Test Method Technical Guide
📐 Scope and Application
This test method covers the determination of Rock Quality Designation (RQD) as a standard parameter in drill core logging, used alongside core recovery values from Practice D2113. The method follows the original calculation by D.U. Deere and applies to core samples from BQ to PQ sizes. RQD denotes the percentage of intact and sound rock in a core interval, defined by the test program, and reflects rock mass quality along the drill hole axis.
This standard does not cover RQD from other borehole methods such as acoustic or optical televiewers. Users must account for drilling and lithologic variations that may affect results, and the standard provides examples of common and unusual scenarios to guide application. All values must conform to Practice D6026 for significant digits and rounding.
⚙️ Test Procedure and Core Requirements
Proper drilling techniques are essential to avoid excess core breakage or poor recovery. The method covers all core barrel types from BQ to PQ, with the original N-size having a diameter of 54.7 mm (2.155 in.). RQD is calculated over a core interval, typically a core run or lithological unit.
RQD Calculation Criteria
| 📐 Parameter | 🎯 Requirement |
|---|---|
| Core Piece Length | Intact and sound pieces ≥ 10 cm (4 in) |
| Measurement Interval | Core run, lithological unit, or other project-defined interval |
| Formula | RQD = (Sum of intact lengths / Total core length) × 100% |
💡 Tip: Drilling techniques must not cause excess breakage or poor recovery. See Section 6.3 of the standard for guidance on avoiding issues that could distort RQD values.
📊 Classification and Reporting
RQD values are classified using the common tunneling system presented by Deere, correlating percentages with rock quality categories.
| 📊 RQD (%) | 🎯 Classification |
|---|---|
| 0 – 25 | Very Poor |
| 25 – 50 | Poor |
| 50 – 75 | Fair |
| 75 – 90 | Good |
| 90 – 100 | Excellent |
Values may be reported in either SI units or inch-pound units, but each system must be used independently. Combining values from both systems may result in non-conformance with the standard. Reporting results in non-SI units is allowed and does not imply non-conformance.
⚠️ Warning: Never mix SI and inch-pound units in calculations or reports. Always specify the unit system used to maintain compliance with Practice D6026.
❓ Frequently Asked Questions
🔍 What is Rock Quality Designation (RQD)?
RQD is a standard parameter indicating the percentage of intact and sound rock in a core interval, based on D.U. Deere’s original method. It is used in geotechnical and mining engineering to assess rock mass quality.
💡 How is RQD calculated?
Sum the lengths of core pieces longer than 10 cm (4 in) within a specified interval, divide by the total core length, and multiply by 100%. The result is a percentage representing rock quality.
⚡ Which core sizes are covered?
This standard covers sizes from BQ to PQ, including conventional N-size core with a diameter of 54.7 mm (2.155 in.). Proper drilling techniques must be used for all sizes to ensure valid results.
📌 Can RQD be determined from televiewer methods?
No, this test method applies only to physical core samples. RQD from acoustic or optical televiewers is not covered and may not produce equivalent data or results.