Curve Parameters

The shape parameters of the grain size distribution curve are determined by the coefficient of uniformity C_U (in [DINENISO14688:2001] and [ASTM D6913] ) and the coefficient of curvature C_C.

U r e s p . C_{u} = \frac{d_{60}}{d_{10}}

Formula:

Calculation of the coefficient of uniformity C_u [Source: STEIN Ingenieure GmbH]

The coefficient of uniformity CU specifies the average inclination (slope) of the grading curve that has been determined according to [ASTM D422] and/or [DIN18123], whereas the coefficient of curvature C_C describes the course of the curve between d₁₀ and d₆₀ :

C_{C} = \frac{{(d_{30})}^{2}}{d_{10} \times d_{60}}

Formula:

The coefficient of curvature C_C describes the curve between d₁₀ and d₆₀. [Source: STEIN Ingenieure GmbH]