Q$.4$ A $6m6m$ square footing is to be constructed at a depth of $5$ m below ground level $($G$.$L$.)$ in sand. The ground water level $($G$.$W$.$L$.)$ is assumed to be $3$ m below ground level. The relevant soil parameters are shown in Figure Q$\mathrm{.}4($a$).$

Figure Q$\mathrm{.}4($a$)$ Shallow foundation

Note: Using the suitable Terzaghi's Bearing Capacity equation with

$N_c=40\mathrm{.}41,N_q=25\mathrm{.}28$ and $N_{}=22\mathrm{.}65.$

$($a$)$ Determine the followings:

$($i$)$ The overburden pressure $(q)$ at foundation level $(D_f)$ and the ultimate bearing capacity $(q_u)$ of the footing.

$(5$ marks$)$

$($ii$)$ If a vertical footing load $($P$)$ of $30000$ kN is applied to the foundation, can the design Factor of Safety $($F$)$ satisfy the minimum required value of $3\mathrm{.}0($i$.$e$.F3?$

$(4$ marks$)$

$($iii$)$ If the designed ground water table $($D$.$G$.$W$.$T$.)$ is assumed to rise to the ground level $($G$.$L$.)$ while the same vertical footing load $($P$)$ of $30000$ kN is applied, can the new design Factor of Safety $(F_{\text{n}\text{e}\text{w}})$ still satisfy the minimum required value of $3\mathrm{.}0($i$.$e$.F_{\text{n}\text{e}\text{w}}3)?$

$(6$ marks$)$

Q$.4$ to be continued....