Geometric constant of circle buried

Geometric constant of a circle in a semi-infinite environment.

Note: $ln(u+\sqrt{u^2-1})=\cosh^{-1}u$

Symbol
$g_u$
Formulas
$u+\sqrt{u^2-1}$IEC 60287-2-1 Ed.3.0 (2023), CIGRE TB 880 Guidance Point 8
$2u$simplification, IEC 60287-2-1 Ed.2.0 (2015)
Used in
$T_{4iii}$