Exercise set
Mine Production Scheduling, Haulage, and Plant Feed Exercises
Solved mine production exercises for stockpiles, haulage capacity, wet roads, crusher utilization, strip ratio, critical path, dry feed and schedule gates.
These exercises focus on executable mine production scheduling: stockpile balance, truck capacity, wet-road derating, crusher utilization, strip ratio, access critical path, plant throughput, moisture-corrected dry feed, conveyor availability, maintenance windows, contingency and schedule release gates. Georesource cutoff, model risk and reconciliation are handled in a separate specialist exercise set.
Use these calculations as planning gates. Real production release requires dispatch data, road condition, equipment availability, maintenance plan, crusher and plant constraints, dewatering and ventilation readiness, slope access, permits, environmental controls, survey pickup and responsible approval.
How to use these exercises
Use the set as an executable-schedule review. Exercises 1 to 4 test stockpile balance, truck capacity, weather derating and required fleet. Exercises 5 to 12 identify crusher, queue, dry-feed, grade, stockpile and conveyor bottlenecks. Exercises 13 to 17 test maintenance, payload shortfall, infrastructure readiness, recovery tonnage and contingency cover. Exercise 18 then converts the schedule into a release or hold decision.
Keep the physical basis visible: wet tonnes versus dry tonnes, ore versus waste, productive hours versus scheduled hours, haulage capacity versus crusher capacity and available stockpile versus reclaimable stockpile. A production target is not a schedule until these bases close together.
Release Evidence Notes
Production evidence should prove that a target is physically executable. Record fleet count, payload, availability, utilization, cycle time, queue state, road condition, plant rate, stockpile cover, maintenance window, water and ventilation constraints, infrastructure readiness and release authority before accepting a schedule.
The evidence package should also show which constraint is controlling. If the plan is limited by trucks, road condition, crusher utilization, conveyor availability, dewatering, ventilation, slope access, ore grade or stockpile cover, the release note should name the constraint and state the permitted target. Otherwise a nominal weekly tonnage can hide an impossible daily sequence.
Engineering Boundary Notes
The exercises below simplify haulage, queueing, stockpiles and plant feed. They do not replace dispatch simulation, maintenance planning, mine design, geotechnical hold points, ventilation modelling, water management or plant control studies.
Real scheduling must include shift calendars, operator availability, tyre and fuel constraints, blast timing, road gradients, ramp congestion, shovel-truck matching, stockpile reclaim geometry, crusher chamber condition, plant downtime, weather, permits, slope exclusion zones and downstream tailings or water constraints. Use the exercises to identify when a plan should be derated before it reaches the shift handover.
Common Release Mistakes
Common mistakes include treating target tonnes as a schedule, ignoring cycle-time variability, overloading the crusher, counting wet tonnes as dry plant feed, assuming stockpile cover without survey, and releasing a shift plan while dewatering, ventilation or access constraints are unresolved.
Other failures include averaging a weekly target across days with unequal access, adding trucks to a congested dump point, counting unavailable maintenance equipment, using planned payload after scale records show underload, and recovering a shortfall by adding tonnage without checking grade, water, road and plant bottlenecks.
Scenario Map
| Scenario | Exercises | Primary check | Engineering decision |
|---|---|---|---|
| Material movement | 1, 2, 3, 4, 7, 16 | Stockpile, truck capacity, wet roads, strip ratio and recovery plan | Adjust fleet, route, target or sequence. |
| Bottlenecks and plant feed | 5, 6, 9, 10, 12, 17 | Crusher, queue, dry feed, grade gate, conveyor and cover | Protect bottleneck or derate schedule. |
| Schedule release controls | 8, 11, 13, 14, 15, 18 | Critical path, maintenance, readiness and release gate | Release, hold or replan the period. |
Exercise 1: Stockpile Balance
A stockpile starts with 48,000 t. Mining adds 22,000 t and the plant draws 30,000 t. Find ending balance.
Solution
Engineering Comment
The balance is positive, but reclaimability and grade segregation still matter.
Plausibility Check
Draw exceeds addition by 8000 t, so the stockpile falls from 48,000 t to 40,000 t.
Exercise 2: Truck Fleet Capacity
Fourteen trucks carry 220 t each, availability is 0.86, utilization is 0.78, scheduled time is 20 h/day and cycle time is 42 min. Estimate daily capacity.
Solution
Engineering Comment
The result has little value unless cycle time and availability come from current dispatch evidence.
Plausibility Check
Capacity near 52,000 t/day is consistent with fourteen large trucks working most of a day.
Exercise 3: Wet-Haul Derate
If wet roads increase cycle time from 42 to 48 min with all other inputs unchanged, estimate daily capacity.
Solution
Engineering Comment
Road condition converts directly into a production loss when payload and available hours stay fixed.
Plausibility Check
Cycle time increases by 14.3 percent, so capacity should fall by a similar order.
Exercise 4: Required Trucks
Target production is 52,000 t/day under the wet-road cycle time of 48 min. Find required physical truck count.
Solution
At least 16 trucks are required; practical dispatch may round higher for standby margin.
Engineering Comment
Adding trucks may increase congestion if the road defect or crusher queue is the real constraint.
Plausibility Check
The current 14-truck fleet is short under wet-road capacity, so the required count is higher.
Exercise 5: Crusher Utilization
Crusher nominal capacity is 2800 t/h. Planned feed is 52,000 t over 20 h. Find utilization.
Solution
Engineering Comment
Utilization above 90 percent leaves little room for oversize, stoppages or feed variability.
Plausibility Check
The planned feed is slightly below the 56,000 t daily nominal capacity.
Exercise 6: Queue-Time Screen
Average truck arrival rate is 32 trucks/h and service capacity at the dump is 40 trucks/h. Find utilization.
Solution
Engineering Comment
An 80 percent queue screen can still create delays when arrivals are bunched by blasting, shift change or dispatch rules.
Plausibility Check
Arrival rate is lower than service rate, so utilization is below 1.
Exercise 7: Strip Ratio and Total Movement
Ore feed target is 18,000 t/day and waste movement is 45,000 t/day. Find strip ratio and total movement.
Solution
Engineering Comment
The fleet must move total material, not only ore feed.
Plausibility Check
Waste is two and a half times ore, so total movement is much larger than plant feed.
Exercise 8: Access Critical Path
Bench access requires dewatering for 3 days, scaling for 2 days and ramp repair for 4 days in sequence. Find release duration.
Solution
Engineering Comment
If the work is sequential, the production plan cannot mine the bench before day 9.
Plausibility Check
The total exceeds the largest single task, 4 days.
Exercise 9: Moisture-Corrected Dry Feed
Wet plant feed is 50,000 t/day at 8 percent moisture. Find dry feed.
Solution
Engineering Comment
Plant metal accounting and throughput limits often use dry tonnes, not wet truck tonnes.
Plausibility Check
The dry feed is 8 percent below wet feed.
Exercise 10: Plant Grade-Quality Gate
Plant feed must be at least 0.60 percent grade. Scheduled dry tonnes are 46,000 t at 0.58 percent. Decide.
Solution
The grade gate fails unless blending or routing changes.
Engineering Comment
Meeting tonnes while missing grade can reduce metal output and distort plant performance review.
Plausibility Check
The comparison is direct: scheduled grade is lower than the gate.
Exercise 11: Stockpile Cover During Delay
The plant needs 11,500 t/day. Usable stockpile is 40,000 t. Access to fresh ore is delayed 4 days. Check cover.
Solution
The stockpile does not cover a 4-day delay.
Engineering Comment
The schedule needs alternate feed, reduced rate or faster access recovery.
Plausibility Check
Four days at 11,500 t/day requires 46,000 t, more than available.
Exercise 12: Conveyor Availability Throughput
A conveyor can move 2400 t/h when running. Availability is 0.92 over 20 scheduled hours. Find daily available throughput.
Solution
Engineering Comment
Conveyor availability can become the bottleneck even when mine fleet capacity is adequate.
Plausibility Check
The result is 92 percent of 48,000 t/day.
Exercise 13: Maintenance Availability Loss
A shovel is planned for 20 h but loses 2.5 h to maintenance. Find effective availability for the shift.
Solution
Engineering Comment
Maintenance windows must be built into the schedule rather than treated as surprises.
Plausibility Check
The lost time is one eighth of the shift, so availability is seven eighths.
Exercise 14: Fleet Payload Shortfall
Planned payload is 220 t, but scale records show 212 t average. For 210 trips, find tonnage shortfall.
Solution
Engineering Comment
Payload shortfall can come from loading practice, material density, truck limits or road conditions.
Plausibility Check
Eight tonnes per trip over a little more than 200 trips gives about 1600 t.
Exercise 15: Readiness Gate
A shift release requires haul road open, pump capacity pass, ventilation pass and crusher available. Results are pass, fail, pass and pass. Decide.
Solution
The release fails because pump capacity is not ready.
Engineering Comment
One infrastructure constraint can make the production schedule non-executable.
Plausibility Check
A release gate with all-required criteria fails when any criterion fails.
Exercise 16: Recovery Plan Rate
A 24,000 t production shortfall must be recovered over the next 6 days. Find additional daily tonnes required.
Solution
Engineering Comment
Recovery tonnage should be checked against fleet, plant, stockpile and permit constraints.
Plausibility Check
Six equal increments of 4000 t recover 24,000 t.
Exercise 17: Contingency Stockpile Days
Required contingency is 3 days at 12,000 t/day. Current contingency stockpile is 31,000 t. Find shortfall.
Solution
Engineering Comment
The plan should not claim three days of cover until the missing 5000 t is available and reclaimable.
Plausibility Check
The current stockpile is below the required stockpile, so a shortfall is expected.
Exercise 18: Schedule Release Gate
A weekly schedule requires fleet capacity at least 52,000 t/day, crusher utilization below 90 percent and stockpile cover at least 4 days. Results are 51,000 t/day, 92.9 percent and 3.5 days. Decide.
Solution
The schedule release fails all three gates.
Engineering Comment
This is not an optimization problem yet; the base schedule is physically overcommitted.
Plausibility Check
Each comparison is unfavorable, so the hold decision is unambiguous.
Validation Package Checklist
- fleet count, payload, availability, utilization and cycle time are current;
- road, pump, ventilation, slope access and plant constraints are checked;
- wet tonnes, dry tonnes and grade basis are not mixed;
- crusher, conveyor and stockpile bottlenecks are explicitly tested;
- maintenance and access critical paths are included in the schedule;
- release decision states target accepted, derated, resequenced or held.
- dispatch, scale, survey and plant records use the same period and material basis;
- stockpile cover is surveyed, reclaimable and grade-compatible with the plant feed plan;
- contingency and recovery plans fit the same fleet, crusher, conveyor and permit constraints;
- shift handover states the active constraint, watch items and trigger for replanning.
The final acceptance question is whether the schedule can survive the first real constraint without becoming a different plan. If the release depends on best-case roads, perfect availability, no queueing and uninterrupted plant operation, the schedule should be derated or resequenced before release.