Stability of Rock Wedges and Excavation Surfaces - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 319

11.4 Stability of Rock Wedges against Rotation

Rotation of a two-dimensional rock wedge supported by one discontinuity
Figure 11.26 shows a two-dimensional rock wedge located at a slope that is supported
by one discontinuity D. The kinematically admissible rotations are described by a unit
vector {r} that lies within the axis of rotation and defines the direction of rotation. Only
the rotation vectors {rl} u } and {r l } lying within the intersections of D with the slope's
crest and the slope and rotation vectors parallel to {rl} u } and {r l } are kinematically pos-
sible. However, pure rotation can only take place if the forces acting on the wedge exert
a moment about a kinematically admissible rotation axis and, in addition, the condition
of equilibrium of forces is fulfilled, that is, if the components of the resulting force {R}
can be carried by the support D (Wittke 1990). As a result, only such rotations can arise
during which the rock wedge remains in contact with D. These are rotations about {r u }
and {r l }.

Figure 11.26 Rotation and stabilization of a two-dimensional rock wedge supported by one
discontinuity