STABILITY OF SLOPE BY METHOD
OFSLICES
Investigate the stability of the slope in Fig. 14 by the method of slices (also known as the
Swedish method). The properties of the upper and lower soil strata, designated as A and
B, respectively, are A—w = 110 lb/ft^3 (17.28 kN/m^3 ); c = O; <£ = 28°; B~w = 122 lb/ft^3
(19.16 kN/m^3 ); c = 650 lb/ft^2 (31.1 kPa); </> - 10°. Stratum A is 36 ft (10.9 m) deep. A sur-
charge of 8000 Ib/lin ft (116,751.2 N/m) is applied 20 ft (6.1 m) from the edge.
Calculation Procedure:- Locate the center of the trial arc of failure passing through
the toe
It is assumed that failure of an embankment occurs along a circular arc, the prism of soil
above the failure line tending to rotate about an axis through the center of the arc. Howev-
er, there is no direct method of identifying the arc along which failure is most likely to oc-
cur, and it is necessary to resort to a cut-and-try procedure.
Consider a soil mass having a thickness of 1 ft (30.5 cm) normal to the plane of the
drawing; let O denote the center of a trial arc of failure that passes through the toe. For a
given inclination of embankment, Fellenius recommends certain values of a and /3 in lo-
cating the first trial arc.
Locate O by setting a = 25° and /B = 35°. - Draw the arc AC and the boundary line ED of the two strata
FIGURE 14