Stability of Slopes - Elements of Soil Mechanics - page 419

Example 13.13: GEO limit state (rotational failure)

Check the GEO limit state for the earth dam described in Example 13.4 using Design
Approach 1, Combination 2.

Solution:

From Table 5.1, the relevant partial factors are: γ φ ′ = 1.25; and γ c ′ = 1 25 . .

′ ′

The design shear strength parameters c d and φ d are determined:

′ =

c 12

1 25

′ =

c = 9 6 . kPa d

γ .

′

c

tan φ ′ tan

.

20
1 25

°

=

=

′ =

φ tan

− 1

tan

− 1

16.2 °

d

γ φ

′

′ ′

(a) Conventional method : Using φ d the conventional analysis is performed and

the calculations are set out in Fig. 13.29.

c d and

π

′ × =

c l 9 6 9 15 . × . × × = 89 136 4 . kN d

180

85 2 136 4
207 9

. + .

Over-design factor, Γ = = 1 07 .

.

Since Γ > 1, the GEO limit state requirement is satisfied.

(b) Rigorous method : The calculations are set out in Fig. 13.30.

Γ = ∑
∑

( )
( )

6
1

237 3
207 9

.
.

Over-design factor, = = 1 14 .

that is, the GEO limit state requirement is satisfied.

Fig. 13.29 Example 13.13 : Conventional method.