The Method OF Slices
this method the potential failure surface, in section, is again assumed to be a
circular arc with centre O and radius r. The soil mass (ABCD) above a trial f
ailure surface (AC) is divided by ve
rtical planes into a series of
slices of width b, as
shown in Figure 9.5. The base of each slice is assumed to be a straight
line. For any slice the inclination of the base to the horizontal is and the
height, measur ed on the centre- line, is h. The analysis is based on the use
of a lumped factor of safety (F ), defined as the ratio of the available shear
strength ( ) to the shear strength (Tm) which must be mobilized to maintain a
condition of limiting equilibrium, i.e.
The factor of safety is taken to be the same for
each slice, implyi ng that there must be mutual support betweenn slices, i.e.
forces must act between the slices.
forces (per unit dim ension normal to
the section) acting on a sli ce are: