Question

A deep cut of 7m has to be made in a clay with unit weight 16$kN/m^2$ and a cohesion of 25 $kN/m^2$. What will be the factor of safety if one has to have a slope angle of ${30}^{\circ }$? Stability number is given to 0.178 (from Taylor's chart) for a depth factor of 3.

• A. 0.80
• B. 1.1
• C. 1.25
• D. 1.0

Answer 1

The correct option is C 1.25

Taylor's stability number

$S_n=\frac{c}{F_c\gamma H}$

$0.178=\frac{25}{F_c\times 16\times 7}$

$F_c=1.25$

Note: Here, there is no use of depth factor = 3

Depth factor, ${\eta }_d=\frac{D+H}{H}$

D = Depth of hard stratum below toe
H = Height of slope above toe