There are plenty of combinations of poor academic performance which result in being kicked out.
Taking the worst case scenario in your first year of uni, if you failed 24 UOC in semester 1, you would be highly recommended to undertake only 6 UOC in semester 2. If you fail that 6 UOC, you are suspended from the university for 1 year. After that 1 year, you come back and do just 6 UOC, if you fail that subject, you are on Provisional Exclusion. Should the uni, for some crazy reason, allow you to enrol in another 6 UOC, and you fail that subject, you will be excluded for 2 years.
Essentially, the quickest way to be excluded is failing 42 UOC in a row or 7 subjects. But this will happen after 3 years.
Or if you just mean suspended, then 30 UOC or 5 subjects BUT in a row.
So there's no certain amount of subjects you have to fail in order to be excluded. It's a combination of poor performance in consecutive semesters which affect your Academic Standing.
https://my.unsw.edu.au/student/academiclife/assessment/academicstandingrulesug.html