We are having an issue with a certain chiller pipe eroding due to soil conditions we are replacing this pipe and I am curious as to whether anyone might provide me with a solution for protecting the tubing from the underground elements. Here are the specifics; piping = 2" copper, ground type = coral rock w/ brackish water infiltration. Thank you for your time and I look forward to reading your responses.

Ouch go with plastic PVC/CPVC or other plastic type tubing. All the problems will go away. Use heavy wall and use sand for the base and topping. Copped and brackish water do not mix well.