Curvature number

The number of curvatures is a characteristic value of soil mechanics to describe the grading curve ( grading curve, grading curve) of a soil . It represents the curvature of the grading curve in the range between 10%, 30% and 60% sieve passage and thus provides information about the frequency distribution of the grain sizes . ${\displaystyle C_{C}}$

The number of curvatures is defined as:

${\displaystyle C_{C}={\frac {{d_{30}}^{2}}{d_{60}\cdot d_{10}}}}$

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 .

The percentiles are mass fractions .

Various properties of non-cohesive soils can be derived from the number of curvatures and the number of irregularities . a. ${\displaystyle C_{U}}$

• the compressibility
• the water absorption
• the sensitivity to frost
• the capillarity
• the gradation of the floor (wide, narrow or intermittent).

In the case of cohesive (fine-grained) soils, these parameters cannot be determined; instead, there are other classification features.

Web links

• Technical University of Munich (Chair for Foundation Engineering, Soil Mechanics, Rock Mechanics and Tunneling): Classification of Soils ( Memento of March 27, 2014 in the Internet Archive ) (PDF file; 478 kB)
• erdbau., p. 46 (PDF file; 35 kB)

Individual evidence

1. ↑ 3.4 coefficient of irregularity Cu and number of curvatures Cc , in study documents geotechnical engineering of TU Darmstadt, XV laboratory and field tests , page 12 (PDF file; 1 MB; accessed on November 26, 2015).