I recommend Stephen Baxter's "Saddlepoint: Roughneck", a novella in three parts, titled "Moon Rain", "Dreams of Rock and Stillness", "The Tunnel Into the Moon".

http://www.isfdb.org/cgi-bin/title.cgi?81868

Summary: Frank Paulis drills a large shaft into the center of the Moon in search of water and succeeds.

http://www.sfsite.com/vault/dave36.htm

Abstract (and paper, for purchase) available here: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo19...