Great article, Used to tunnel when I was at UT back in the late 70's. Security was not so strick back then, there were no motion detectors like they have now. It was a matter of visiting all the old buildings on campus and checking out the lower level for a way in. Found a way in via Jester and the Physics building which were not locked for over a year.
You mentioned forgotten storage, Welch was a bonanza of old stuff.
The steam tunnels meet in a large intersection underground. They didn't have all the gates you mentioned back then.
I see you found the beach. It has changed a bit. Used to be a favorite hangout and grafetti spot. It used to be a fallout shelter long ago complete with signs and it even had dry food stored there. Its under Moore Hall. For some reason the word got out about the tunnels. I don't remember why but by 1980 it was not safe to go down there for several years as far as getting caught.