Theoretically, the pressure from the fault would cause one or more rupture discs to blow.
A few years ago I was commissioning an AIS ring bus with 345 kV SF6 breakers. All of our breakers were open. The remote end had energized the line and had soaked for about 5 minutes. I went outside to check the voltages at the CCVT & VT box for the line and we heard what sounded like a flag pole "clanking". My CCVT voltages disappeared. The CCVT/VT secondary boxes were about 12 feet from the failed breaker.
The center phase had flashed over phase to ground. Fault records from the remote end (about 1 mi away) indicted ~28kA, with ~ 3cycle clearing time (411L relays, 2 cycle breakers). Locally, some reported seeing the center phase of the line gallop. The voltage dip was so pronounced that a large automotive plant across the way tripped off line (fed from 138kV).
After verifying that my underwear was clean, I inspected the GCB. The rupture disc was intact, with no visible damage to the GCB. Compared to the other phases, the cement pad appeared darker, which we speculated was due to exterior moisture on the tank being thrown off from the forces of the fault. An SF6 sample was drawn with about 200 ppm SO2.
The OEM replaced the failed phase and took the failed unit to the factory for analysis. About eight months and 15 emails asking for the analysis, the OEM reported internal contamination as the root cause. These particular type of breakers are shipped from the factory with the bushings installed and a small positive SF6 pressure. FWIW, Doble tests were performed on each breaker as part of the commissioning tests and the results from this breaker were no different than the sister units.