kornstørrelser

Kornstørrelser refers to the size of individual grains within a material, such as soils, sediments, powders, or crushed rock. The grain size distribution (GSD) describes the share of grains across size classes and is a key characteristic in geology, engineering and material science. It is usually presented as a cumulative distribution curve or as a histogram, and summarized with percentiles (for example D10, D50, D90) and with measures of sorting (uniformity) and skewness.

Classification scales: A widely used system in geology is the Wentworth scale, which partitions particles into clay, silt, sand and gravel with approximate boundaries: clay smaller than about 0.004 mm, silt 0.004–0.0625 mm, sand 0.0625–2 mm, and gravel larger than 2 mm. For soil texture classification, many laboratories use the USDA (or equivalent) ranges: clay < 0.002 mm, silt 0.002–0.053 mm, sand 0.053–2.0 mm; exact limits can vary by standard.

Measurement methods: Coarse fractions are commonly separated by dry or wet sieve analysis. Fine fractions are determined by hydrometer or pipette methods, or by laser diffraction in modern laboratories. The choice of method depends on the material and the required resolution.

Applications: Knowledge of grain sizes informs compaction and permeability in geotechnical engineering, drainage and water retention in agriculture, sediment transport and depositional history in geology, and powder flow and packing in materials science.

Terminology: Sorting describes the spread of grain sizes; D50 is the median size; D10 and D90 indicate finer and coarser tails. Grain-size data are essential for characterizing materials and predicting behavior under mechanical or hydraulic load.