Tunnel Boring & Heavy Civil Equipment worked example

Disc Cutter Wear Rate at 99% target cutter survival rate: a worked example

Push target cutter survival rate up to 99% and the picture changes. This example computes every intermediate figure at that operating point. Use it when disc cutter wear rate in tunnel boring and heavy civil equipment needs a clean rate and gap-to-target you can put on a tier board.

The inputs for this scenario

  • Disc cutters worn beyond limit: 8 count (unchanged)
  • Total disc cutters inspected: 250 count (unchanged)
  • Target cutter survival rate: 99 % (raised for this scenario; the documented default is 95)

Working through the calculation

  • Applying the documented formula (Disc cutter wear rate = disc cutter wear rate count ÷ total disc cutter wear rate population × 100) to the inputs above produces each figure below.
  • At this operating point the engine returns 3.2 % for disc cutter wear rate, the number this scenario is built around.
  • At this operating point the engine returns 95.8 points for disc cutter wear rate gap to target.
  • At this operating point the engine returns 8 count for disc cutter wear rate count.
  • At this operating point the engine returns 250 count for total disc cutter wear rate population.

How this compares with the baseline

  • Against the tool's baseline example, where target cutter survival rate sits at 95% and the headline result is 3.2 %, this scenario lands almost exactly on the baseline at 3.2 %.
  • It computes the percentage of inspected disc cutters that are worn beyond their limit and the gap between that rate and your target cutter survival percentage. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Disc cutter wear rate: 3.2 % (headline result)
  • Disc cutter wear rate gap to target: 95.8 points
  • Disc cutter wear rate count: 8 count
  • Total disc cutter wear rate population: 250 count

Run it with your numbers

  • Every input above is editable in the live Disc Cutter Wear Rate calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.