Rock strength properties and their measurement - Rock Slope Engineering: Civil and Mining - page 94

Table 4.2 Sources of shear strength data plotted in Figure 4.21

Point
number

Material Location Slope height

(m)

Reference

1 Disturbed slates and

quartzite's

Knob Lake, Canada — Coates et al . (1965)

2 Soil Any location — Whitman and Bailey

(1967)

3 Jointed porphyry Rio Tinto, Spain 50-110 Hoek (1970)

4 Ore body hanging

wall in granite rocks

Grangesberg, Sweden 60-240 Hoek (1974)

5 Rock slopes with

slope angles of
50-60 ◦

Any location 300 Ross-Brown (1973)

6 Bedding planes in

limestone

Somerset, England 60 Roberts and Hoek

(1972)

7 London clay, stiff England — Skempton and

Hutchinson (1969)

8 Gravelly alluvium Pima, Arizona — Hamel (1970)

9 Faulted rhyolite Ruth, Nevada — Hamel (1971a)

10 Sedimentary series Pittsburgh, Pennsylvania — Hamel (1971b)

11 Kaolinized granite Cornwall, England 75 Ley (1972)

12 Clay shale Fort Peck Dam, Montana — Middlebrook (1942)

13 Clay shale Gardiner Dam, Canada — Fleming et al . (1970)

14 Chalk Chalk Cliffs, England 15 Hutchinson (1970)

15 Bentonite/clay Oahe Dam, South Dakota — Fleming et al . (1970)

16 Clay Garrison Dam, North Dakota — Fleming et al . (1970)

17 Weathered granites Hong Kong 13-30 Hoek and Richards

(1974)

18 Weathered volcanics Hong Kong 30-100 Hoek and Richards

(1974)

19 Sandstone, siltstone Alberta, Canada 240 Wyllie and Munn

(1979)

20 Argillite Yukon, Canada 100 Wyllie (project files)

One of the early difficulties arose because
many geotechnical problems, particularly regard-
ing slope stability analysis, are more conveniently
dealt with in terms of shear and normal stresses
rather than the principal stress relationships of
the original Hoek-Brown criterion, defined by the
equation:

is the uniaxial compressive strength of the intact
rock material and m and s are material constants;
s 1 for intact rock.

An exact relationship between equation (4.13)
and the normal and shear stresses at failure was
derived by J. W. Bray (reported by Hoek, 1983)
and later by Ucar (1986).
Hoek (1990) discussed the derivation of equi-
valent friction angles and cohesive strengths for
various practical situations. These derivations
were based upon tangents to the Mohr envel-
ope derived by Bray. Hoek (1994) suggested
that the cohesive strength determined by fitting
a tangent to the curvilinear Mohr envelope is

=

σ ci m σ 3 s 0.5 σ 1 = σ 3 +

σ ci +

(4.13)

where σ 1 and σ 3 are respectively the major and
minor effective principal stresses at failure, σ ci