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

Chapter 6 SLOPE STABILITY
Fill
Fill
Firm
soil
Sliding
Thin Seam of
Weak
Clay
Material of
General Low
Permeability
Sliding
Lens of
Sand
without Friction
Fill
Sliding
Shallow Layer of Weak Soil
Firm
Soil
Figure 6.2 Sliding Block Failure Mechanism
6.2.3
Circular Arc Failure
All of the limit equilibrium methods requiree that a potential slip surface to be assumed in order to
calculate the factor
of safety. For computational simplicity the slip
surface is often assumed to be
circular, particularly
for relatively homogeneous soil condition. Calculations are repeated for a
sufficient number of trial slip surfaces to
ensure that the minimum factor of safety has been
obtained.
Circularr arc failure occurs when
the ground sink down and the adjacent ground rises and the failure
surface
follows a circular arc as
illustrated in Figure 6.3. This type
of failure shall be discussed in
more detail in this chapter as it is a very
common mode of failure especially
in river bank and
embankment in soft ground.
Figure 6.3 Example of Circular Arc Failure Mechanism
6-2
March 2009