Question $2(50\%)$

Please explain in details and make sketches if necessary. a$)$ For the slope shown in the figure given below, fill in the blanks of the provided solution

table and determine the factor of safety against sliding for the trial slip surface AC$.$ Use the

ordinary method of slices for the solution and ignore tension cracks. Assume the groundwater

table is vertically $4m$ below the slope surface and water pressures as in infinite analysis.

b$)$ Analyze the stability of a $3m$ deep shallow failure on the surface of this slope if its $c^{\text{'}}$

decreases to $7$kPa due to rainfall infiltration. Assume the groundwater level rose by $2m$

$($vertical distance$).$