- 2059 Chaitra (old course) · 4 marks
Rotary versus percussion drilling
Short answer
Rotary drilling uses a rotating bit with downward pressure to cut rock and recover continuous core, suitable for hard rock and deep holes. Percussion drilling lifts and drops a chisel bit to crush material, yielding only disturbed cuttings, and is slower, shallower, and cheaper, used for hard soils and boulders.
Differentiate between rotary drilling and percussion drilling.
| Basis | Rotary drilling | Percussion drilling |
|---|---|---|
| Action | Rotating bit with downward pressure cuts the rock | Heavy chisel bit is lifted and dropped to crush the rock |
| Bit | Diamond, tungsten carbide or roller bit | Chisel or star-shaped steel bit |
| Material drilled | Hard rocks and also soils | Hard soils, gravel, boulders and rock |
| Sample | Continuous solid core recovered | Only crushed cuttings (disturbed) |
| Circulating fluid | Water or drilling mud/air removes cuttings | Water added, cuttings removed by bailer or sand pump |
| Speed | Fast and smooth | Slower |
| Depth and accuracy | Deep holes, good alignment | Shallower, less accurate |
| Cost | Higher | Lower |
| Use | Dam, tunnel and bridge investigation | Water wells and shallow investigation |
✓ Answer checked by Claude Opus 5.5 (high effort)
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