Don't try epoxy, it's a mess waiting to happen.
As Casual Shooter said, hire someone to come out for a quick x-ray of the slab. Those cables are usually spread pretty far apart. You can also get anchors that only go in 2 inches or so but will keep the safe rock solid.
Also, what time of home are you in that requires post-tension cables in your foundation? Do you have a large expansive basement under the slab?