New Construction variations after completing works

Hi Team,
I building 2 townhouses in Victoria , after paying lock up stage invoice, builder raised huge variations ($140k) which were completed works during slab as well as frame stage which never send to sign before completing the works.
I signed standard HIA contract. Big variations referring Rock removal of site cost, another few referring not in plans, need to change during construction to complete works etc....
Does anyone come across same issues and any advise will be valuable