Irregularity number

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C U > 15 very uneven ground
C U = 5-15 uneven ground
C U <5 uniform soil

The uniformity coefficient (uniformity coefficient; earlier ), including unequal granularity number or -grad called, is a dimensionless characteristic value of soil mechanics to describe the particle size distribution curve (grading curve, grain size curve) of a soil . It provides information on how uniformly the grain sizes of a soil are distributed .

The number of irregularities is defined in DIN EN ISO  14688-2: 2004 as the ratio of the diameter d 60 with a sieve passage of 60% to the diameter d 10 with a 10% sieve passage:

With

  • d x = grain size (diameter) at x% of the mass passage of the grading curve, d. H. x% of the mass of the soil have a smaller grain size and pass through a sieve with a mesh size  d x .

This ratio represents the gradient of the grain size curve in the range between 10% and 60% of the sieve passes. The percentiles are mass fractions .

There is also a degree of irregularity wherever similar things of different sizes are compared with one another. It generally denotes the ratio of the large (or largest) to the small (or smallest):

In mechanical engineering , the degree of irregularity of a drive , e.g. B. an internal combustion engine , the speed fluctuation with periodic movements; it expresses the fluctuation of the angular velocity during a working cycle, whereby the drive must be constantly loaded with uniform torque . However - unlike described above - the largest is not related to the smallest value, but the difference that occurs is related to the arithmetic mean :

literature

  • Gerd Möller: Geotechnics. Soil Mechanics, 2nd edition, Wilhelm Ernst & Sohn, Berlin 2013, ISBN 978-3-433-02996-1 .
  • Wolfgang Förster: Mechanical properties of unconsolidated rocks. BG Teubner, Stuttgart 1996, ISBN 978-3-8154-5000-0 .

See also

Web links