Which method is used to sample from a stockpile to prevent sloughing?

Sampling from a stockpile requires careful techniques to ensure that the sample accurately represents the entire stockpile without causing material displacement or sloughing. The method of inserting a flat board horizontally into the stockpile is effective because it minimizes disturbance to the material. By doing this, the flow of the material is contained, reducing the chance of sloughing which may occur if the stockpile is altered too significantly.

Using a flat board helps create a barrier that allows for the collection of a specific sample without creating a void or leading to a collapse of the surrounding material. This technique maintains the integrity of the stockpile while allowing for a representative sample to be collected from various depths.

In contrast, other methods like shoveling from the top can disrupt the stockpile significantly and lead to unintended sloughing. Using a vibrating screener or making cuts into the stockpile might also disturb the materials, risking the uniformity of the sample. Thus, inserting a flat board horizontally stands out as the most suitable method to ensure minimal disturbance during the sampling process.