Shear Strength Applications in Plastic and Limit Equilibrium - Unsaturated Soil Mechanics in Engineering Practice - page 639

1.5

1.0

C

1 : 2 Slope

0.5

0.0

0 0.5 1

Dimensionless x-coordinate

(a)

(a)

Center of slip surface
x = 30
y = 23

(14.8, 20) (25, 20)

n

(30, 10) (38, 10)

(b)

(b)

Figure 12.74 (a) Interslice force function for (b) a deep-seated
slip surface computed by switching on gravity forces.

Figure 12.76 Va l u e s o f C and n coefficients for interslice force
function: (a) C versus slope angle; (b) n versus tangent of slope
angle.

Figure 12.75 illustrates the definition of the dimension-
less distance ω . Elastic, finite element functions have been
computed for slip surfaces which are circular. However, the
shape of the function is quite similar for composite slip sur-
faces. The magnitude of the C parameter varies with the
slope angle, as does the n variable (Fig. 12.76).

or F f appear on both sides of the equations, with the factor
of safety being included through the normal force equation
(i.e., Eq. 12.77). The nonlinear factor-of-safety equations
can be solved using an iterative technique. The factors of
safety with respect to moment and force equilibriums can be
calculated when the normal force N on each slice is known.
The computation of the normal force requires a magnitude
for the interslice shear forces X L and X R and an estimate
of the factor of safety F s .

12.5.11 Solving Factor-of-Safety Equations
The factor-of-safety equations with respect to moment and
force equilibriums are nonlinear. The factors of safety F m

Figure 12.75 Definition of dimensionless distance ω for interslice force function.