What does "mean grain size" refer to in geology?

What does "mean grain size" refer to in geology?

• A. 25% passing size of aggregate
• B. 50% passing size of aggregate
• C. 75% passing size of aggregate
• D. 100% passing size of aggregate

Answer: (B)

Mean grain size in geology typically refers to the statistical measure of the average size of grains in a sediment or aggregate sample. Specifically, it is defined as the particle size at which 50% of the aggregate is finer and 50% is coarser, often referred to as the median grain size. This value provides a useful indication of the overall texture of the sediment or aggregate, influencing its engineering properties, such as permeability and strength. In sedimentology and geotechnical applications, the mean grain size is important for understanding the behavior of materials under different conditions, such as water drainage or compaction. The 50% passing size directly correlates with these characteristics, making it a key parameter for engineers and geologists in both natural formations and man-made structures. The other choices incorrectly represent different percentiles in the grading curve of aggregates. For instance, the 25% passing size corresponds to a coarser measure, while the 75% and 100% passing sizes refer to finer or full retention sizes respectively. These values can be useful for specific applications but do not denote the mean grain size, which is specifically the 50% passing size.

Mean grain size in geology typically refers to the statistical measure of the average size of grains in a sediment or aggregate sample. Specifically, it is defined as the particle size at which 50% of the aggregate is finer and 50% is coarser, often referred to as the median grain size. This value provides a useful indication of the overall texture of the sediment or aggregate, influencing its engineering properties, such as permeability and strength.

In sedimentology and geotechnical applications, the mean grain size is important for understanding the behavior of materials under different conditions, such as water drainage or compaction. The 50% passing size directly correlates with these characteristics, making it a key parameter for engineers and geologists in both natural formations and man-made structures.

The other choices incorrectly represent different percentiles in the grading curve of aggregates. For instance, the 25% passing size corresponds to a coarser measure, while the 75% and 100% passing sizes refer to finer or full retention sizes respectively. These values can be useful for specific applications but do not denote the mean grain size, which is specifically the 50% passing size.