Question No$.4$

$[12$ marks$]$

a$)$ For the central footing shown in Figure $2$ above, assume the groundwater table is known to fluctuate periodically, $2ft$ and $8ft$ below the ground surface.

Note, The Layer $1$ soils properties are as determined from question $3$ above; Angle of internal friction, $\frac{O}{?}=?$

Cohesion, $c=l\frac{b}{f^2}$

Unit weight $of$ soil, $=120l\frac{b}{f}{t}^3$

i$)$ Find the extreme allowable loads that can be imposed on this square footing due to the changing environment assuming a factor of safety of $2\mathrm{.}5.$

$10$

ii$)$ Which load would you recommend for design and why

$2$