When sampling from a stockpile, what method yields representative samples?

• A. Create horizontal surfaces with vertical faces in the top, middle and bottom thirds, and obtain samples from the horizontal surface near the intersection with vertical faces
• B. Sample only the top surface
• C. Sample randomly from a single point on the pile
• D. Sample only from the bottom third

Answer: (A)

Sampling a stockpile to be representative means gathering material from across different depths and locations so the mix reflects the whole pile, not just one part. If you only sample the top surface, bottom layers, or a single point, you’ll bias the result toward whatever characteristics those limited areas show, which might miss differences in size distribution, moisture, or fines that exist elsewhere in the pile.

The approach described does this thoroughly: you establish sampling planes at the top, middle, and bottom thirds and take samples from the horizontal surface near where each plane intersects the pile’s vertical faces. This way you’re collecting material from multiple depths and from different parts of the surface, capturing any variation that occurred during stacking and settlement. When you combine these samples, you get a composite that better represents the entire stockpile.

Other methods fall short because they isolate one zone or a single point, which tends to misrepresent the overall material due to segregation and spatial variability.