Question $1(15$ Marks$)$

Figure $1$ shows a layer of granular soil in a tank in which water flows downwards $($left$)$ seepage and upward $($right$)$ seepage

a$.$ Derive the effective stress at point $C$ in both cases $(10$ marks$)$

b$.$ Explain how the seepage of water through the soil medium either in the upwards direction or the downward directions influences effective stress. $(3$ marks$)$

c$.$ Discuss the difference between permeability and seepage. $(2$ marks $)$