Stability of Rock Wedges and Excavation Surfaces - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 301

For stability, limit equilibrium at the external and internal failure lines of each block
must be fulfi lled. The state of limit equilibrium on the external failure lines of each
block i can be formulated analogously to (11.11) as
(11.28)
Figure 11.12 Sliding of a rock mass on a polygonal surface (Kovari & Fritz 1984)
Figure 11.13 Rock mass supported by two or more discontinuities forming a multi-block system
bounded by external and internal sliding planes