Principle and application
Core drilling is rotary drilling that advances through rock and very hard soils, cutting the material with a diamond core bit and recovering a continuous core. The core reveals the degree of fracturing, the rock mass quality (RQD) and the elevation of sound rock, exactly where percussion drilling can no longer advance.
The test in stages
Rotary drilling
The string rotates with a diamond bit, cutting the rock by abrasion.
Core recovery
The core barrel recovers the continuous core of the rock mass.
Logging and RQD
Recovery and RQD are measured, indicators of rock quality.
Core boxing
The core is arranged in boxes labelled by depth.
The test in the field
According to rotary · RQD
| Core | Continuous sample of rock / hard soil |
|---|---|
| RQD | Rock quality designation index |
| Recovery | Percentage recovered per run |
| Fracturing | Degree and orientation of discontinuities |
Quality and field operation
Data quality
- Bits and core barrels suited to the rock mass.
- Recovery and RQD control per run.
- Core photographed and boxes labelled.
- Geological description by a qualified professional.
Site standard
- Qualified for high-compliance areas: mining, industry and ports.
- Organised, signed work front with an HSE procedure in place.
- Own crews and fleet, including night shifts.
The deliverable
| Drilling log | Profile with recovery, RQD and rock mass description |
|---|---|
| Core boxes | Arranged and photographed by depth |
| Bearing elevation | Indication of the rock head / hard layer |
| Typical lead time | According to depth and rock hardness |
Sectors and project types
Frequently asked questions about core drilling
What is core drilling used for?
Core drilling is rotary drilling that advances through rock and very hard soils, cutting the material with a diamond core bit and recovering a continuous core. The core reveals the degree of fracturing, the rock mass quality (RQD) and the elevation of sound rock, exactly where percussion drilling can no longer advance.
What is RQD?
Rock Quality Designation: the sum of core pieces longer than 10 cm divided by the length drilled. It is the classic indicator of rock mass quality.
Are core drilling and mixed drilling the same?
No. Mixed drilling starts with percussion (SPT) in the soil and switches to rotary (core) drilling on reaching rock, combining both methods in the same borehole.
Recovery and RQD: reading rock mass quality
Technical bulletin on interpreting cores from rotary core drilling.
Core drilling for your project
Tell us about your project and we will prepare the investigation plan and the quote.