Note: No Handwritten solution. Also, please provide complete solution.

Question:

A trench is excavated at the silty$-$clay site. The trench collapsed following excavation. You are to consider the point $5m$ beneath the ground surface marked in Fig. $1\mathrm{.}2.$ You can assume the soil is dry with a dry unit

weight of ${}_g^{\text{d}\text{r}\text{y}}=18k\frac{N}{m^3}.$

Prepare a diagram that explains how the soil at that point could have failed following excavation of the trench. Your diagram must include a labelled plot of the Mohr's circles that illustrate the stress state at the marked point in the soil before and after the excavation, the strength envelope.

You are encouraged to briefly annotate the diagram to help you illustrate failure. Any calculated values of stress should be included in your diagram.

$($a$)$ Before excavation

$($b$)$ After excavation

Figure $1\mathrm{.}2$: Schematic of the site before and after the excavation of a trench. The point of interest is marked by the orange spot