Constraints on DTH Drill Efficiency in Soft Rock

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  1. Even with low hardness, soft rock limits DTH drill efficiency. In f=1-2 clay, speed depends on slag removal. Paste-like cuttings block channels.
  2. Drill pressure transfer drops from 90% (hard rock) to 55%. Reduce impacts from 350 to 250/min to cut cuttings. Soft rock’s “plastic flow” causes hole collapse.
  3. Maintain ≥0.6MPa flushing pressure, raising air compressor energy by 30%. Slag blockages cause 22% downtime in clay.

 

Clay “envelops” drill bits, wrapping alloy teeth. Cutting ability drops 40%; clean bits every 30 minutes.