Hydraulic Structures: Fourth Edition

regarding this very low value for zu). Major principal stresses (equa-

tions (3.37a) and (3.37c)) are

1u0.03 MN m^3

and

1d0.56(10.25)0.70 MN m^2.

Worked Example 3.2

The overturning stability factor of the dam in worked example 3.1 is to

be revised to FO1.6 to improve the stress distribution and obviate

cracking. The foundation is unable to take prestressing anchorage loads,

and a downstream supporting shoulder of compacted rockfill is to be

added as suggested in Fig. 3.23. Determine the height of rockfill shoulder

required.

Compacted rockfill.Unit weight, (^) r19 kN m^3 ; coefficient, K 0 (esti-
mated)0.60.
Solution
FO1.60 (equation (3.19)).
Hence,∑M



required from shoulder(1.623 110) 28 2968680 kN m^1.

Therefore,



K 0

2

rh^2



h

3



2

rh



(0.5

3

h)^2

 8680

and

0.141h^3 8680/19

givingh14.8 m, say 15 m.

∑M







∑M



184 CONCRETE DAM ENGINEERING