The Delft Sand, Clay & Rock Cutting Model, 2019a

Basic Soil Mechanics.
soil characteristics with little or no equipment. It is thus an extremely useful tool for identifying spatial variation
both within and between plots (fields) as well as identifying progressive changes and boundaries between soil
classes and orders.
The method involves taking a small sample of soil, sufficient to roll into a ball of approximately 2.5 cm diameter,
from just below the surface. Using a small drop of water or 'spit' the sample is then moisten to the sticky point (the
point at which it begins to adhere to the finger). The ball is then molded to determine its workability and its class
according to the steps in the chart opposite.
Soil separates are specific ranges of particle sizes. In the United States, the smallest particles are clay particles and
are classified by the USDA as having diameters of less than 0.002 mm. The next smallest particles are silt particles
and have diameters between 0.002 mm and 0.05 mm. The largest particles are sand particles and are larger than
0.05 mm in diameter. Furthermore, large sand particles can be described as coarse, intermediate as medium, and
the smaller as fine. Other countries have their own particle size classifications.
Table 2-1: Soil Classification.
Name of Soil
Diameter Limits (mm)
Clay 200
Figure 2-4: Soil failure (www.4isfge.org).
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