How to Design a Pit Ramp
The ramp is the pit's aorta — every ton, every shift, forever, on one strip of engineered rock. Undersize it and the whole mine queues behind the mistake for a decade. Here are the design rules, with the reasoning that makes them stick.
01Set width from the widest truck
The standing rule: running width ≈ 3.5× the widest vehicle for two-way traffic (1.5–2× for single-lane with turnouts). A 24-ft-wide haul truck wants ~84 ft of running surface — before the berm and ditch. Total ramp real estate = running width + safety berm + drainage, commonly 100–120 ft for big iron. Design for the biggest truck you'll ever buy, not the one you own.
02Hold grade at 8–10%, sustained
Most operations design 8% (1V:12.5H) sustained, tolerating 10% for short pitches. Steeper saves ramp length but murders cycle times uphill, brakes downhill, and tires always — and in wet or icy climates, 10% loaded downhill is where retarders go to die. Grade is the one parameter you can't cheaply fix later: it's cast in the pit walls.
03Berm to the axle
Safety berms at mid-axle height of the largest truck (roughly half the tire diameter) on every open edge — commonly 4–6+ ft for ultra-class fleets. A berm a truck can climb over is landscaping, not protection, and it's one of the most-cited deficiencies on surface inspections.
04Engineer the corners and switchbacks
Widen in curves (trucks off-track), flatten the grade through switchbacks (target ≤2–4% in the turn itself — a loaded truck starting uphill from a stopped switchback on 10% is a clutch of misery), and superelevate modestly for drainage and stability. Sight distance rules everything: no crest or corner should hide a pickup from a hauler at speed.
05Build the surface and the water together
Cross-slope 2–4% to a ditch on the wall side, culverts before the water wins, and a running surface of compacted crusher-run over structural fill — soft ramps eat tires and transmissions invisibly. Rolling resistance is a permanent tax: every 1% of extra RR costs like an extra 1% of grade, and it's the reason a motor grader on the ramp is the best-paid machine in the pit.
06Reserve the ramp real estate early
Ramps consume pit wall — a spiral ramp sterilizes rock behind it on every level it crosses. Locate ramps in final walls where possible, plan the crossover points, and remember: relocating a ramp mid-life means re-mining your own pit. The best ramp design is the one done before the first bench, with the last bench in mind.
ShotRock designs and audits haul systems — ramp geometry, cycle simulation, and the $/ton case for the fixes — with a PE-track engineer's signature behind the drawings.
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