  The goal of this note is to announce certain results in orbit equivalence
theory, especially concerning the approximation of p.m.p. standard equivalence
relations by increasing sequence of sub-relations, with applications to the
behavior of the Bernoulli percolation on graphs at the threshold pu. R\'esum\'e
en Fran\c{c}ais. Approximations de relations d'\'equivalence standards et
percolation de Bernoulli \`a p\_u.
