ABSTRACT
The various forces that are acting on the wedge are shown in Fig. 11.17(a). As the pressure face AB moves away from the backfill, there will be sliding of the soil mass along the wall from B towards A. The sliding of the soil mass is resisted by the friction of the surface. The direction of the shear stress is in the direction from A towards B. If Pn is the total normal reaction of the soil pressure acting on face AB, the resultant of P
n and the shearing stress is the active pressure P
a making an
angle 8 with the normal. Since the shearing stress acts upwards, the resulting Pa dips below the normal. The angle 8 for this condition is considered positive.
