The tube does not contain the pressure. Consider what happens to a tube is you put 8bar into while not mounted inside a wheel+tire...... If the tire cannot contain the pressure, the tube explodes, but it is that lack of conatainment that causes it.
Problem is the tire or the rim. This cna be caused by :
- Tire / rim mismatch
- Rim Faultly
- Tire faulty
- Tire incorrectly installed
We know its not 1). Have a look at the rim and check for faults and damage. Then inspect the tire for a faulty bead or tear. It may not be visible (A broken bead can be hard to see but can usually be felt.).
In your case, it looks like the bead has separated and you need a new tire.
Another likely cause in my mind is incorrect mounting. Install a new tube, pump it up, let it down and pump it up again to full pressure - all the time watching whats happening to the shape of the tire. Any sign of deformity, you need to investigate.
Edit: Information provided in the OPs comments indicate the rim has failed rather catastrophically (Fault 2. in the list) - I incorrectly assumed the strip was off the tire. You have a coice - if you don't want to buy a new wheel (at least rim, but a made up wheel is often cheaper) you don't have to - you just won't be able to ride the bike... I suspect what happened is the the rim was damaged by either riding with the puncture or during the repair, and has developed a crack. The stress from the ire pressure was too much for it. Another possibility is you put more pressure into the tire than the rim is rated for - however they should handle 8bar.
I would strongly recommend a new tire and tube for the replacement rim........