The disrupted rock should have DCR around 10 or so, with integral parts only half foot in a column of test cylinder extracted of 5 ft. Then I would look it mainly as gross gravel of the same material.
I was actually looking more for the strength of the bond between the rock and concrete. I am assuming that the rock can resist lateral forces and that lateral pressure is not develped against the pile. Therefore, the method of using lateral pressure x tan (external frictions angle) would not be valid.
Then you have two limits: the shear strength near the altered surface within the rock, and the bond strength from concrete.
Tensile strength in the rock uses to be 10 to 15% percent of compressive atrength, and shear strength is not thought to be very dissimilar. DCR=10 woulg give allowable pressure of contact of around 2 MPa, 12.5% of which is 0.25 MPa, allowable, for shear strength.
For a DCR=10 you can estimate from correlations c=0.255 MPa coexisting with an angle of inner friction of only 15 deg sexagesimal.
Bond within the concrete in uncheckable area better not to be taken over 1 MPa ultimate, 0.66 MPa allowable.
