This massive, ancient tortoise likely doesn't care a bit about a group of adventurers, not even noticing if they are underfoot.
The PCs in my current campaign encountered one of these. Where it had been sleeping, they found the remains of a crushed house, and in the basement space were the remains of another group of adventurers that never got out when the tortoise decided to go to sleep years earlier.
This thing is really only dangerous to treants, things that are in its path, and creatures that try to hurt it.