# Distance d of multi-layer backfill

Distance d to calculate the resistance of multi-layer backfill.

Symbol
$d_{b4}$
Unit
m
Formulae
$\sqrt{{s_{b4}}^2+{w_{b4}}^2}$
Related
$s_{b4}$
$w_{b4}$
Used in
$R_{q21}$
$R_{q31}$