The factor |1 - β(6)| is dependent on soil properties and depth of laying as well as the cable or duct diameter.

The values quoted in IEC 60583-1 Table IV are for a depth of burial of 1.0 m and a soil thermal diffusivity of 0.50E-6 m2/s. These values may be used for cable or duct depths within the range 0.75 to 1.5 m. For any other depth of burial or value of soil thermal diffusivity the numerical value may be obtained from the equation below.

However, the software does not need this factor as it calculates the factors $β_{t}$ for a single cable or $γ_{t}$ for $N_{c}>1$ by using the corresponding equations for $τ$ between 1 and 6 hours.

Symbol
$\beta_{\mathrm{6}}$
Unit
-
Formulae
$- \left|{- \frac{\operatorname{expi}{\left (- \frac{D_{\mathrm{o}}^{2}}{16 \delta _{\mathrm{soil}} \tau} \right )}}{2 \ln{\left (\frac{4 L_{\mathrm{cm}}}{D_{\mathrm{o}}} \right )}}}\right| + 1$
Related
$D_{\mathrm{o}}$
$\delta _{\mathrm{soil}}$
$L_{\mathrm{cm}}$