I've seen it twice with very, very bad results (condense building up in the tubes and finally resulting in a good isolator)
Pictures already posted in the past here on RE.
They installed a tube that went even higher than the roof so that a natural convection took place.
Air under the soil should be colder then ambient.
How the flow will be? Difficult to predict: will depend on conditions outside/conditions soil, wind direction and speed around the building creating a negative or a positive pressure.
I should never do this again, radiant heating is safer, cheaper and better, in fact perfect controllable.
If you want to install an air net, Install tubes and connect it all to a fan so that air can be forced through it.