hi sam Similar blasting has been done when benching in large underground caverns. Generally if the blasting is controlled well enough not to make a mess of the rock in the wall above, then there is no problem with regard to damage to rock support. May be useful to consider smooth blasting to get a better finish to the upper bench rock face and less loosening on discontinuities. I presume that rock anchors will be grouted, whether cement or resin - ungrouted mechanical shell anchors would come loose. Rock anchors, tensioned or not, depend on face plate and nut to secure near surface rock possibly aided by mesh and sprayed concrete depending on frequency of joints. Fly rock may damage face plate and nut if blasting is poorly designed. Blast mats e.g. old conveyor belting or tyres and cable) may be used to suppress fly rock.