Engineering Rock Mechanics

Question and answers: foundation and slope instability mechanisms 289

Case d: as (a) but with rock wedge between failure regions through intact

Case e: plane sliding of single wedge formed by fracture.

Casef: failure in intact rock and along fracture.

These six mechanisms can be used to develop criteria for foundation
failure, taking into account the possibilities of failure both through the
intact rock and along the fracture planes.
This leads to more complex derivatives of the 'single plane of weak-
ness' concept that was discussed in Chapter 7 for uniaxial loading of a
single fracture in a rock specimen.

rock.

417.2 Consider extending the method of equilibrium analysis for
plane failures (see Q16.3) to the case of retaining walls. The failing
block, ABC in the sketch below, is restrained in three cases by the
application of load to the vertical face, AB:
(a) by a horizontal force of magnitude T acting through the centroid
of the block;
(b) by a horizontally acting uniform pressure distribution p from the
top of the face to the point where the failure plane daylights; and
(c) by a pressure distribution varying linearly from zero at the top
of the face to q at the point where the failure plane daylights.