In the video below i look at the use of the Radial Surface Model in combination with normal TIN Surface Models to model the floor area, vertical faces of a large rock cut and the top area of the rock cut to compute the Rock Excavation volumes. The volume computation can be carried out using the Corridor Model once the finished grade model for the rock surface is created using surface instructions.
Video shows some of the techniques - the project is not a finished article but hopefully provides some valuable pointers on the techniques to use