Page 271 - Rock Mechanics For Underground Mining
P. 271

Figure 9.13  (a) Tetrahedral key
              block in the crown of an excavation
              with a flat roof (b) Projection of unit
              cell on to a reference plane (c) Projec-
              tion of unit cell and key block-forming
              region on to the plane of cross-
              section of a square excavation (after
              Kuszmaul, 1999).









                                                                        253
   266   267   268   269   270   271   272   273   274   275   276