Building Design and Construction Handbook - Merritt - Ventech!

6.78 SECTION SIX
FIGURE 6.34a Gravity and semigravity
retaining walls. (From NAVFAC DM-7.2,
1982.)
for the wall friction between granular soil and wood or concrete walls and � � 20�
for the wall friction between granular soil and steel walls such as sheet-pile walls.
Note in Fig. 6.35 that when wall friction angle � is used in the analysis, the active
earth pressure resultant force (P A) is inclined at an angle equal to �.
Additional important details concerning the active earth pressure are as follows:
1. Sufficient Movement. There must be sufficient movement of the retaining wall
in order to develop the active earth pressure of the backfill. For dense granular
soil, the amount of wall translation to reach the active earth pressure state is
usually very small (i.e., to reach active state, wall translation � 0.0005 H, where
H � height of wall).
2. Triangular Distribution. As shown in Figs. 6.34 and 6.35, the active earth
pressure is a triangular distribution and thus the active earth pressure resultant
force (P A) is located at a distance equal to 1 ⁄3H above the base of the wall.
3. Surcharge Pressure. If there is a uniform surcharge pressure (Q) acting upon
the entire ground surface behind the wall, then there would be an additional
horizontal pressure exerted upon the retaining wall equal to the product of k A