Rule of thumb is 1/4 of the axial capacity of the pile. The reasoning is, when the pile is load tested the ram used to produce the axial force is anchored onto four outer piles, therefore the upward reaction on each support pile is 1/4th the tested axial compressive force. However, I would also check with the Geotech.
I think it depends on how far your pier is socketed into the rock. You'll be able to pull a little more on a pier 6 feet socketed into the rock instead of one socketed 6 inches in rock.
I've seen a report that recommended using 150 psi as the bond strength between the concrete and rock interface.
What type of rock are you dealing with?? Is a Solid or Fractured? Have you done any testing on it? 150psi as an allowable bond strength could be a little on the high side.
