II$.$ Effective stress $(30$ points$)$

Consider the site shown below.

For the three scenarios described below, determine the total stresses, pore pressures, and effective stresses at a depth of $12\mathrm{.}5$ m from the ground surface:

a Hydrostatic conditions

b When a piezometer installed at the top of the gravelly sand layer indicates that the water inside it rises to $1$ m below the ground surface

c At time $=0^{-},$ time $=0^{+},$ and six month after a fill of sand is added on top of the clean sand to raise the ground surface elevation. The added fill is $4$ m in thickness, and it has a total unit weight of $16k\frac{N}{m^3}.$ Assume double drainage conditions for the clay layer.