2nd year exams Watch
Theoretically speaking I am guessing civil engineering has quite high entry requirements into to third year, (I think it is 6 C's?) So if you are unable to reach that you would be required to re-sit the year (or subsequently the modules you failed). Sometimes you can be lucky and be more lenient and they might let you in if you have high enough re-sit grades but that rarely happens. It is very unlikely that they will chuck you out, in less obviously your attendance is incredibly low but even then it is low probability of getting kicked out.
I would not be afraid to email your mentor, they are there to listen to your concerns!