Page 61 - RoadCem Manual - PCT BV
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A visual inspection can roughly determine what the sub-base is composed of. There are locations where, as a result of erosion many grooves and thin fractions occur. This requires a certain insight into the causes of erosion.
Boulders, gravel, sand, silt and clay fractions are grouped according to the grain size. Erosion occurs from water, and/or wind streams.
Figure 4.6 Wind erosion, Grand Canyon . Figure 4.7 Water erosion.
The biggest grains are found mainly in the mountains where the river originates. The smaller, finer grains are found in the valleys of the mountains in the part of the river where the water flow is less.
Figure 4.8 Origin, Large grain. Figure 4.9 Fine grains at the mouth of the river.
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