Problem $3$: The results of two CD tests on overconsolidated clay are given in the following table:

Use a graphical method to obtain answers to the following. You may use algebraic equations to check your answers

if you wish, but only a graphical solution is required.

a$)$ Calculate the shear strength parameters of the soil. Here "strength parameters" can refer to drained

and$/$or undrained friction angle and$/$or cohesion. Depending on the type of test, you can determine some

or all of these parameters. Determine all that you can based on the type of test for which data is given.

b$)$ If you increase the chamber confining pressure to $130$kPa and once again run an experiment under CD

conditions, what do you predict is the major principal stress at failure?

c$)$ What orientation to you predict for the plane on which failure will occur?