Sieve analysis is a procedure to quantify the sizes and types of particles present in a particular soil sample as well as their relative frequency of occurrence. The analysis can be performed on inorganic materials, such as gravels or aggregate mixtures as well. The sample is sifted through a series of sieves, beginning with a sieve with large apertures, through successively smaller sieves. The results of a sieve analysis can tell geologists and engineers much about the composition of a sample and how a particular soil or other mixture will behave in civil engineering and construction settings.
A sieve is a simple device consisting of a frame designed to hold material and a bottom made of wire mesh. The gaps in the mesh determine the size of particles that can pass through it. Sieves are classified according to any one of several standards. Most standards use a number to classify individual sieves that corresponds to the number of openings in 1 linear inch (2.54 cm) of mesh.
The various standards can vary slightly, and as the diameter of the wires used can affect the size of the openings, there are a very large number of possible combinations and sizes. This means that two sieves classified as size 10 may pass particles of different maximum sizes. This must be taken into consideration by the tester, and the sieve sizes as well as the standard used must be noted in the resulting report.
The results of a sieve analysis are given as a list of the percentage of the test sample, by weight, that passes through each sieve. For example, the first, largest sieve may pass 95% of the total sample by weight, the second may pass 85%, and so on. By analyzing this data, it is possible to quickly see the relative composition of a particular sample with regard to the distribution and frequency of particle sizes.
To trained and experienced engineers and geologists, this data represents valuable information about how a particular soil or other mixture may behave under a variety of conditions, including compaction, settling, and shifting. Landslide risk and the behavior of flood waters, particularly in regard to how soils may absorb them can be assessed using sieve analysis data along with other information. Decisions about civil engineering and construction projects often rely heavily on this kind of data. Other uses for sieve analysis data can involve agriculture, environmental impact studies, watershed management, and land-use decisions.
