Stacker-reclaimer vs conveyor dump: what the pile shape tells you

Walk the imagery of any bulk terminal or mine stockyard and you'll see two families of pile. One is long, flat-topped, and ridged along its length. The other is a cone, or a cluster of cones, with no particular orientation. The difference isn't cosmetic. It tells you how the material got there, and that in turn tells you how much you can trust a volume estimate off the top of the pile.

Chevron and windrow stacking: what the ridge line means

A stacker-reclaimer laying coal, iron ore fines, or concentrate in chevron mode runs back and forth along a fixed boom radius, dropping material in a straight line that builds up in overlapping triangular lifts. The result is an elongated ridge with a roughly uniform cross-section down its length, shaped like a loaf rather than a cone. Windrow stacking is the same idea with the boom slewing to lay multiple parallel ridges side by side, often used where reclaim needs to blend across several lifts at once for grade control.

Both methods leave a signature: straight, parallel crest lines, consistent width, and a cross-section that doesn't change much whether you measure it at the 20-metre mark or the 200-metre mark. Know the stacker's design cross-section, even roughly, from the pile's own geometry, and a short strip of the ridge gets you to a volume for the whole thing. Week-to-week changes in ridge length or crest height read as draw-down or build-up without much guesswork.

Chevron stacking also segregates material by particle size, coarser lumps roll to the toe, fines stay near the crest, which is exactly why mines that need consistent blend switch to windrow or chevcon (chevron plus reclaim-by-cone) methods instead. None of that changes how the pile reads from above, but it's worth knowing when a sudden shift from chevron ridges to a cluster of cones shows up in the imagery. That's usually not a stacking preference change, it's often a signal the operator has gone to truck dump because the stacker is down, or because the lot is small enough that mobile plant makes more sense than firing up the boom.

Conical stockpile vs elongated stockpile: reading a truck dump

A conveyor-fed truck dump or a mobile stacker working a small lot builds cones. Material drops from a fixed or roughly fixed point and runs down the angle of repose in all directions, so you get a pile that's circular or near-circular in plan view, steep-sided, and irregular where multiple dump points overlap. Run several dump cycles at slightly different spots and you get a cluster of overlapping cones rather than one clean shape, which is a much messier thing to turn into a volume number than a uniform ridge.

A single cone gets you most of the way to a volume number from base diameter and crest height alone, the same rough arithmetic bulk material handlers have always used eyeballing a yard. A cluster of overlapping, uneven cones won't give you that shortcut. The footprint changes shape between passes as new dumps bury old slopes, so comparing week one to week two means comparing two different geometries, not the same ridge a little taller or shorter. That's the practical reason conical pads need more frequent passes to keep a trend reliable, and why an index built on actual pile geometry, rather than a flat footprint-times-average-height guess, holds up better at sites running mixed dump and stacker operations.

Why the stacking method matters for an inventory read

None of this is really about which method a yard prefers. It's about what the shape does to the error bars on a volume estimate. An elongated chevron or windrow pile gives you a repeatable cross-section and a trend line you can track with confidence. A conical pad built by truck dump or mobile stacker gives you a shape that shifts with every load, and reading stockpile tonnage trend off that shape without accounting for the geometry is where a lot of back-of-envelope estimates go wrong.

If you're trying to turn pile geometry at a named site into a clean weekly series instead of eyeballing satellite stills, that's the problem Bulk Stockpile Index was built to solve. Take a look at how the weekly CSV handles both pile types before your next inventory call.