The idea behind this build is simple: Shen can already teleport and he turns the tide of team fights wherever he appears. This build is made to create the tankiest Shen while also optimizing his ability to be everywhere.

RUNES:
Shen isn't very rune dependent so i went with flat Health and CDR to make his teleport a little more spammable and give him early game tanking ability.

MASTERIES:
Maxing defensive masteries just makes sense on a tank, and the magic pen. is nice for your Vorpal Blade.

SPELLS:
Teleport seems redundant at first; after all, he already has a teleport. The trick here is that by alternating teleports, you can switch lanes, get items at base, etc. WITHOUT your teleport being on cooldown. Never be absent from a teamfight and never be out of lane; ideally, you should never need to walk between lanes unless you're patrolling the jungle or chasing someone.
Revive is one of the least-respected spells, especially on tanks (who are, ideally, never supposed to die), but combined with teleport it becomes a different skill altogether. If you never die in a game, you will never use revive, but if you never die in the game it probably doesn't even matter that you have a wasted summoner skill. Die even once, though, and Revive becomes worthwhile. TIP: DON'T SPAM IT. Save it for either (1) returning to a team fight you get knocked out of early, ult-protecting a carry, and helping finish off the fight (if they focus you first only to have you pop in 5 seconds later it can RUIN a team fight for your opponent, esp. since Shen is a great tower-diver) or (2) recovering from a cheap, low-level (this works best before 10th level) gank by your tower by throwing Revive and Teleport, and using the HUGE speed boost and extra 200hp from the mastery to chase down the (presumably weakened) enemy.

ITEMS:
Start with Dorans or health crystal depending on preference
Build boots early (i like boots of mobility for easy chasing but if the other team has much magic damage/CC swap it for mercury's treads
Get an early Aegis; it's good for you and makes the whole team happy
Sunfire Cape adds tankiness and passive dps
Frozen Mallet is useful for more health and the slow
Force of nature rounds out the magic resist and gives health regen
And finally, Atma's impaler makes taking all that health do something for your damage output

Augments to this build could be to swap out either the mallet or the FoN in favor of a Rylai's or some other tank item (like more armor and resist).