Engineering Rock Mechanics

288 Foundation and slope instability mechanisms

I

Figure 17.3 The slope stability and the associated analysis is a function of the rock type.

(a) Granite slope in a building stone quarry. (b) Chalk slope in a road cutting.

instabilities induced by the pre-existing fractures. Instabilities through

the intact material are best tackled using soil mechanics principles, for

which the reader is referred to Bromhead (1992)

17.2 Question and answers: foundation and slope

instability mechanisms

417.1 The diagram below (Serrano and Olalla, 19982) shows six
basic potential mechanisms by which failure can occur beneath a
foundation on a fractured rock mass containing one fracture set,
indicated by the fine shading. Failure can occur through the intact
rock, indicated by the letter R, and/or along a fracture plane, indic-
ated by the letter R Describe the six basic mechanisms illustrated.

A 17.1 The mechanisms are as follows.

Casea: failure occurs through rock mass by creation of new failure

Case b: as (a), but with rock wedge also formed by failure along fractures.

Case c: as (a), but with rock wedge formed by fractures below loading

surface in intact rock.

area.

' Bromhead E. N. (1992) The Stability of Slopes. Blackie Academic, London, 2nd edn.
The diagram is from Serrano A. and Olalla C. (1998) Ultimate bearing capacity of an
anisotropic discontinuous rock mass, Part I. Basic modes of failure. Int. I. Rock Mech. Min.
Sci., 353, 301-324.