Civil Engineering Reference
In-Depth Information
Figure 24.3
Principal types of retaining structure.
failures of the structural elements. The walls in Fig. 24.4(a) and (b) are failing because
there are very large distortions in the soil in front of and behind the wall. In Fig. 24.4(c)
and (d) a gravity wall may fail by sliding, overturning or by exceeding the limiting
bearing pressure at the toe. In Fig. 24.4(e) any retaining wall may fail by slipping below
the wall but this is really a problem in slope stability (see Chapter 21). In Fig. 24.4(f) the
base of an excavation may fail by piping and erosion due to seepage or by movement of
the soil. Figure 24.5 illustrates structural failures of the wall or an anchor or buckling
of props.
24.5 Stress changes in soil near retaining walls
It is helpful to consider the total and effective stress paths in soil near retaining walls
during and after construction to examine whether the undrained or long-term drained
cases are most critical. For retaining walls it is necessary to separate those loaded
by excavation from those loaded by filling. (Note that I am continuing to use load-
ing to mean an increase of shear stress irrespective of what happens to the normal
stresses.)
