Exercise #$3$:

For a direct shear test on a dry sand, the following are given $($specimen size are $50$ mm $50mm25mm)$:

$\backslash$table$[[$Test No$,$Normal Load $($N$),$Shear force at failure $($N$)],[1,200,100],[2,333,178],[2,422,245],[3,489,288]]$

$1-$ Draw a graph for the shear stress at failure against normal stress,

$2-$ Determine the angle of shearing resistance $($i$.$e$.$ angle of friction$)$ from the graphs.

$3-$ For a normal stress of $150k\frac{N}{m^2},$ what shear force is required to cause failure in the specimen?