Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 7 RETAINING WALL
Figure 7. 5 Development of Rankine
Active and Passive Failure Zones for a
Smooth Retaining Wall
When the
Rankine state of failure has been reached, active and passive failure zones will develop as
shown in
Figure 7.5. The coefficient of active
and passive
earth pressure are expressed by the
following
equations:
- -
-
(7.3)
-
- -
(7.4)
Where
= the sloping angle of the backfill behind the wall
a = the active
earth pressure coefficient
p = the passive earth preesure coefficient
= the effective frictional angle of the soil
K a
K p
φ Note that for the case
of cohesionless soil on level backfill, thesse equations are reduced to
Ka =
-
tan 2 (45 -
)
(7.5)
Kp =
-
tan 2 (45 -
)
(7.6)
Thus, without considering the ground water level, the distribution of lateral earth pressures can be
assumed
to be triangnular (see Figure 7.6) such
that
7-6
March 2009