Energy Loss Mechanisms of DTH Drills in Hard Rock

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  1. Brenda hard rock (f>8), DTH drill energy efficiency stays below 30% (65% in soft rock). 55% of impact energy goes to rock elastic rebound.
  2. 15% becomes friction heat between bit and rock; only 30% breaks rock effectively. Hard rock causes hydraulic “pressure pulsation”.
  3. Pressure fluctuates 18-25MPa, dropping pump efficiency from 85% to 60 (15% extra loss). Drill pipe vibrates 15mm (3mm in soft rock).

 

Vibration resonance adds 8-10% to total energy loss. Drilling 1m f=10 granite uses 28kWh—4.2x f=2 soil. 62% of this energy is ineffective.