Generally, the correlations suggest that the friction angle for a coarse sand is greater than that of a fine sand with similar relative densities.
That's the problem (at times) with using correlations. You can get into real trouble if you aren't careful. Frequently, the biggest difference between a uniform coarse sand and a uniform fine sand (of the same material) is the particle shape. The smaller particles
tend to be less angular as a result of more weathering. But this isn't always the case -
The major factors that affect the soil angle of internal friction are particle shape, density, grain size distribution, composition, particle strength, and stress history. And not necessarily in that order.
The angle of repose is affected by the particle shape and grain size distribution. But the angle of repose is
not the angle of internal friction. In fact, there is no such thing as
the angle of internal friction...
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