Drilling through hard rock costs more per meter because it is slower, tougher on equipment, and more energy‑intensive than drilling through soft soil. Every extra hour on site, worn bit, and litre of fuel gets baked into the contractor’s per‑meter rate.
1. Slower penetration rates
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Hard rock drills much more slowly than sand, clay, or loose overburden, so the rig spends more hours achieving the same depth.
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Because most contractors price to cover machine time, crew wages, and fuel, more hours per meter directly increase the cost per meter.
2. Higher wear on tools and consumables
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Rock rapidly wears out drill bits, hammers, rods, and other consumables, which must be repaired or replaced more often.
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To stay profitable, contractors load this extra wear‑and‑tear into the per‑meter price for hard‑rock sections.
3. Greater energy and fuel consumption
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Penetrating rock requires higher thrust, torque, and in many cases compressed air or heavy drilling fluid, all of which increase fuel and power usage per meter.
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Higher energy consumption per meter translates into higher operating costs, which appear as a higher unit rate.
4. Need for more specialized equipment
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Hard‑rock drilling often needs stronger rigs and down‑the‑hole (DTH) or similar systems, which are more expensive to buy, run, and maintain than light rigs used in soft ground.
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The capital cost and maintenance of this heavier equipment are recovered by charging more per meter where those tools are required.
5. Increased operational risk and downtime
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In hard formations, the risks of bit jamming, tool breakage, deviation, or lost equipment are higher, leading to unplanned downtime.
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Contractors typically pad hard‑rock rates to cover these risks so that a single problematic hole does not wipe out their profit across a project.
6. Possible need for additional handling and safety measures
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Working in rock can generate more vibration, noise, and cuttings management issues, sometimes requiring extra handling or safety controls.
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Any additional handling, cleanup, or safety requirements add labour hours that are reflected in the per‑meter price.
Overall, drilling in hard rock compresses more time, fuel, consumables, equipment wear, and risk into every meter drilled. By contrast, soft soils allow faster penetration with lighter gear and less wear, so the contractor can offer a lower rate per meter while still covering their costs.