3. Active wedge. The active wedge is defined as that zone of soil involved in the development of the
active earth pressures upon the wall. This active wedge must move laterally in order to develop the
active earth pressures. It is important that building footings or other load carrying members are not
supported by the active wedge, or else they will be subjected to lateral movement. Figure 11.3
shows an illustration of the active wedge of soil behind the retaining wall. As indicated in Fig. 11.3,
the active wedge is inclined at an angle of 45° + f/2 from the horizontal.
Active wedge