Problem $3(1\mathrm{.}5$ points$)$

Consider the upward flow of water through a layer of sand in a tank as shown in Figure $3.$ For the sand, the

following are$-$given: void ratio e$=0\mathrm{.}45$ and specific gravity of solids G$\_($s$)=2\mathrm{.}65.$ And, given: H$\_($I$)=1$m$,$H$\_(2)=$

$3$m$,$h$=1\mathrm{.}2$m$,$z$=1\mathrm{.}5$m$.$

a$.$ Determine the vertical effective stress at point B and C $.$

b$.$ What should be the value of h to cause boiling?

Figure $3$