Stability of Rock Wedges and Excavation Surfaces - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 328

(11.103)

where E IR is Young's modulus of the intact rock and I is the axial geometrical moment
of inertia of the cubical-shaped rock column being

(11.104)

Thus, the buckling stress can be calculated as (Hoek & Brown 1980b, Wittke 1990)

(11.105)

Figure 11.33 Buckling of rock columns at a wall of a cavern (Wittke 1990)

In this case horizontal discontinuities (D3) are assumed. However, because of limited
tensile strength of the rock mass it is unlikely to assume that the rock mass column is
fi xed at one end (Euler case 1) which would lead to a smaller buckling stress

σ b . Equa-
tion (11.105) can therefore also be used in cases where no horizontal discontinuities are
present.