$(5)$ A long strip footing having a width of $2\mathrm{.}0ft$ is to be constructed $3\mathrm{.}0ft$ below the ground surface. Underlying the footing is sand having bearing capacity factors of $Nc=0,N=25,Nq=20.$ The unit weight of sand is $120l\frac{b}{f}{t}^3.$ Considering a factor of safety of $2\mathrm{.}5,$ the gross allowable bearing capacity of the footing is most nearly:

$($A$)3\mathrm{.}1ksf$

$($B$)3\mathrm{.}5ksf$

$($C$)4\mathrm{.}1ksf$

$($D$)4\mathrm{.}5ksf$

Answer:

$2.$ Calculation and Short Answer Questions $(20$ Pts$)$

$(1)(5$ pts$)$ A consolidated$-$drained $($CD$)$ triaxial test on a normally$-$consolidated $($NC$)$ clay yielded a friction angle $\frac{O}{?},$ of $30.$ Assume the cohesion intercepts $c=c^{\text{'}}=0$kPa. If the confining pressure during the test was $150$kPa.

$($a$)(2$ pts$)$ What is the deviator stress at failure?

$($b$)(2$ pts$)$ Determine the normal effective stress and shear stress on the plane of failure

$($c$)(1$ pts$)$ Determine the angle of failure plane from the horizontal plane.