  This paper introduces some methods to determine the simultaneous
approximation constants of a class of well approximable numbers
$\zeta_{1},\zeta_{2},...,\zeta_{k}$. The approach relies on results on the
connection between the set of all $s$-adic expansions ($s\geq 2$) of
$\zeta_{1},\zeta_{2},...,\zeta_{k}$ and their associated approximation
constants. As an application, explicit construction of real numbers
$\zeta_{1},\zeta_{2},...,\zeta_{k}$ with prescribed approximation properties
are deduced and illustrated by Matlab plots.
