(Solved): 6. (a) During a civil engineering construction work, it is planned to cut a 70 slope, 12m high ...

6. (a) During a civil engineering construction work, it is planned to cut a $70^{?}$ slope, $12\mathrm{m}$ high, measured vertically in soil having a unit weight of $19.5\mathrm{kN}/{\mathrm{m}}^3$, with an effective cohesion of $38.4\mathrm{kN}/{\mathrm{m}}^2$ and an effective angle of friction of $15^{?}$. Neglecting all possibility of seepage through the embankment, determine the factor of safety with respect to cohesion. (b) When will failure occur in a slope formed in a cohesionless soil and a cohesive soil?