(Solved): The figure shows the cross-section of a proposed cutting in cohesive soil. The undrained shear stre ...

The figure shows the cross-section of a proposed cutting in cohesive soil. The undrained shear strength $\left({\mathrm{C}}_{\mathrm{u}}\right)$ may be taken as $25\mathrm{kPa}$ in the upper layer and $42\mathrm{kPa}$ in the lower layer; the unit weight is $19\mathrm{kN}/{\mathrm{m}}^3$ and the friction angle is zero in both layers. a. (20 points) Determine the factor of safety passing through the toe. b. (80 points) Previous soil explorations showed that a firm stratum layer was located at a depth of $[\mathrm{H}/4$ to $\mathrm{H}]?\mathrm{m}$ below the toe. For each depth determine the FS for a circle tangent to elevation of each $[\mathrm{H}/4$ to $\mathrm{H}]\mathrm{ft}$; and evaluate the FS.