A naturally occurring soil sample may have particles of various sizes.
Over the years, various agencies have tried to develop the size limits
of gravel, sand, silt, and clay.
For a basic understanding of the nature of soil, the distribution of the
grain size present in a given soil mass must be known. The grain-size
distribution of coarse-grained soils (gravelly and/or sandy) is determined ...
For engineering purposes, soil is defined as the uncemented aggregate of mineral
grains and decayed organic matter (solid particles) with liquid and gas in the empty
spaces between the solid particles.