Forget about cutting through a post-tensioned slab.

1) If you hit a cable someone could get seriously hurt.
2) When a cable gets cut your foundation is seriously compromised.
3) The only reason a post-tensioned foundation is installed is when the soil quality is bad.

As an architect I would suggest thinking of something else.
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“Always remember the 6 P’s”
(Prior Preparation Prevents [censored] Poor Performance)