Final answer:
The sieve number that separates coarse from fine-grained soils is the #200.
Step-by-step explanation:
The sieve number that separates coarse from fine-grained soils is the #200.
Sieve numbers are used to classify soil particles based on their size. In the U.S., the ASTM (American Society for Testing and Materials) standard is commonly used, which assigns a number to each sieve size. The lower the sieve number, the coarser the soil particles, while the higher the sieve number, the finer the soil particles.
In the case of coarse and fine-grained soils, the #200 sieve is used to separate them. Coarse-grained soils have larger particles, such as gravel and sand, which will be retained on a #4 or #10 sieve. Fine-grained soils have much smaller particles, such as silt and clay, which will pass through a #200 sieve.