Question $6.$

Continuation from Question $5.$ The soil you collected from a depth. You know the load coming you're

your structure. Using Influence Factor $($Boussinesq$\text{'}$s Equations$)$ method you calculated that for your

structure the vertical stress in soil is $52$Kpa with $12$Kpa horizontal stress $($confining stress due to

surrounding soil$).$ Figure is shown below:

You want to see if the soil has enough strength to take this vertical stress.

a$.$ Draw the Mohr Circle for this stress orientation.

b$.$ Even though at this orientation there is no shear stress, but if you keep rotating there will be at

certain plane where your soil will have maximum shear and your soil will fail at that plane. What

will be the maximum shear demand on your soil due to this loading?

c$.$ From Question $5,$ you have your shear envelop equation. You can calculate what will be your

shear strength for $52$ Kpa vertical stress. Verify whether your soil will fail due to structural

loading $($shown in the figure above$).$

d$.$ Calculate normal stress, $$ and shear stress $$ at plane which makes $30$ degrees with horizontal.Question $5.$

You have collected soil sample from your site which is predominantly silty soil. Because of your budget

constraint, you decided to calculate the strength of your soil using Direct Shear Test. You soil sample is

cylindrical in shape with $100mm$ in height and $25mm$ in diameter. The loading was very slow, ensuring

that there is no pore water pressure development within the specimen. The following data were

recorded.

Calculate Cohesion coefficient, C$,$ and friction angle, $$