Stability of Rock Wedges and Excavation Surfaces - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 302

where i and i-1 are the contact forces per meter that act on the internal failure lines,
Di are the lengths of the external failure lines and

φ Di,d and c Di,d are the design values
of the shear parameters of the discontinuities Di i which form the external failure lines
(Figs. 11.13 and 11.14). Using the notation in Fig. 11.14 the components of the line
forces Gi, i , P i and

i normal and parallel to the external failure lines are

(11.29)

(11.30)

(11.31)

(11.32)

(11.33)

(11.34)

Figure 11.14 Forces acting on block i (Fig. 11.13)

Insertion of (11.29) to (11.34) into (11.28) and solving for i yields: