The major strategy on CWR is pretensioning, but there are also multiple kinds of expansion joints used in different circumstances. I’m not saying it’s impossible to do the same with a vacuum chamber, but I am saying there’s no simple reliable answer, and certainly no answer so obvious and bulletproof that it doesn’t even require testing before you could start construction.

Elon Musk either didn’t know or didn’t care that his company wasn’t doing the required engineering and testing to make a real functioning hyperloop.