  Let $\Delta$ be a simplicial complex. We study the expansions of $\Delta$
mainly to see how the algebraic and combinatorial properties of $\Delta$ and
its expansions are related to each other. It is shown that $\Delta$ is
Cohen-Macaulay, sequentially Cohen-Macaulay, Buchsbaum or $k$-decomposable, if
and only if an arbitrary expansion of $\Delta$ has the same property. Moreover,
some homological invariants like the regularity and the projective dimension of
the Stanley-Reisner ideals of $\Delta$ and those of their expansions are
compared.
