Productivity & Owning and Operating Cost of Equipment Notes

Last reviewed 16 Sept 2026 · 7 min read

Soil volume changes

State	Meaning
Bank measure (BCM)	Volume in the natural, undisturbed state
Loose measure (LCM)	Volume after excavation — increases due to voids
Compacted measure (CCM)	Volume after compaction — usually less than bank volume

FormulaSwell, load factor and shrinkage

Swell $= \frac{V _{l oose} - V _{bank}}{V _{bank}}$ → $V_{l oose} = V_{bank} (1 + swell)$

Load factor $= \frac{V _{bank}}{V _{l oose}} = \frac{1}{1 + swell}$

Shrinkage $= \frac{V _{bank} - V _{co m p a c t e d}}{V _{bank}}$ → $V_{co m p a c t e d} = V_{bank} (1 - shrinkage)$

Hauling units carry loose volume; payment is generally for bank (excavation) or compacted (fill) volume.

Equipment output

FormulaProduction of cyclic equipment

Q = q \times K \times \frac{3600}{t _{c}} \times E (per hour)

$q$ = rated (heaped) bucket capacity; $K$ = bucket fill factor (depends on material); $t_{c}$ = cycle time in seconds; $E$ = job efficiency (e.g. 50 working minutes per hour → $E = 50/60 = 0.83$ ). Convert loose output to bank volume with the load factor.

Cycle time

Fixed time — loading, dumping, turning, spotting, accelerating/decelerating (nearly constant).
Variable time — haul and return travel, depending on distance and speed.
Cycle time = fixed time + haul time + return time.

Factors affecting productivity

Type and condition of material (digging difficulty, moisture).
Operator skill; machine condition; matching of equipment.
Haul road condition, grades and distance.
Angle of swing and depth of cut (for shovels and draglines — output is maximum at the optimum depth of cut and falls with larger swing angles).
Weather, altitude, management (job efficiency).

Matching hauling units with loaders

FormulaNumber of trucks

Number of bucket loads per truck $= \frac{truck capacity (loose)}{q K}$ (rounded) Loading time $=$ number of buckets × loader cycle time Truck cycle time $T =$ loading + haul + dump + return + spot and wait Number of trucks for balanced fleet $N = \frac{T}{loading time}$

Choosing fewer trucks (round down) makes the loader wait; more trucks (round up) make trucks wait — choose the option with lower cost per unit output.

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