Retaining Structures - Elements of Soil Mechanics - page 249

Fig. 8.20 Pressure distribution in strutted excavation.

In Fig. 8.20b , the shape A ′ B ′ C ′ D ′ represents, to an enlarged scale, the original form of the surface that
has yielded to the position ABCD of Fig. 8.20a ; the resulting pressure on the back of the wall is roughly
parabolic and is indicated in Fig. 8.20c .
For design purposes a trapezoidal distribution of the form developed by Terzaghi and Peck (1967), since
revised by Terzaghi, Peck and Mesri ( 1996 ) is assumed. The design procedure for the struts is semi-
empirical. For sands, the pressure distribution is assumed to be uniform over the full depth of the excava-
tion (Fig. 8.20d ). For clays, the pressure distribution depends on the stability number, N:

= γ

H
c u

N