(Solved): The angle of friction of a sand is \( \phi^{\prime}=28^{\circ} \). Given that the deviator stress ...

The angle of friction of a sand is \( \phi^{\prime}=28^{\circ} \). Given that the deviator stress at failure is \( \sigma_{1}-\sigma_{3}=23 \) psi during a CD test, answer the following questions (note that there are many ways to solve the following problems, so be as creative as you like): (a) What assumptions can we make, given that we are dealing with a drained sand? Specifically, what does this tell us about the cohesion of the soil and the pore water pressure? (5 pts.) (b) Find critical angle at which failure occurs. (5 pts.) (c) What is the maximum shear stress that occurs during failure? What are the minor and major principal stresses? What is the stress (shear and normal) on the plane of failure? (10 pts.)