Stability of Rock Wedges and Excavation Surfaces - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 297

(11.17)

Thus, the minimum required anchor force for stability is obtained if φ D,d .

The stability proof of a two-dimensional wedge bounded by two discontinuities D1
and D2 located at a sidewall of a tunnel, as illustrated in Fig. 11.9, can be carried out
analogously.

α =

Figure 11.9 Stabilization of a two-dimensional rock wedge located at the sidewall of a tunnel or cavern

The stability of a two-dimensional rock wedge bounded by a discontinuity and a vertical
open tension crack subjected to self-weight and water pressure, illustrated in Fig. 11.10,
was investigated by Hoek & Bray (1977). The crack of depth z is assumed to be fi lled
with water up to a level of z w z. The water pressure is assumed to increase linearly with

depth in the crack and to decrease linearly along the discontinuity D from its maximum
at the intersection of the crack with the discontinuity, to zero at the surface of the slope
(Fig. 11.10). The water pressure distribution acting on the sliding surface is described by
the line force W 1 . The water pressure distribution acting in the crack can be treated like
a horizontal external line force W 2 with the following components normal and parallel
to the sliding plane:

≤

(11.18)

(11.19)