I really can't understand why slab track is not used here. How many times has the ballast been washed away over the years? I did hear that, this storm aside, there is a full time PW gang on the section just to maintain all the issues that arise on it.
How is the concrete slab going to be supported?
What happens when those supports are washed away/undermined?
How long would the line be closed while the supports/slab is repaired compared to the current method of throwing some ballast in the hole? Current breach excepted because that certainly isnt normal.
Concrete slab track is only normally used where the underlying ground doesnt move (tunnels etc), that certainly isnt the case at Dawlish.