Mike
The first point is to define the reason for your rock cover:
- pipeline protection from dropped object, vessel grounting, anchor impacts etc...
- additional submerged weight wrt upheaval buckling in the case your pipe is hot or high pressure.
Then you need to determine the height of cover required
Then depending of the type of rock you ll dump and the vessel which is going to do it, your cover profile can be defined.
As this point you need to engage discussion with rockdump contractors.
R