Problem $6\mathrm{.}12*$ A clay sample is isotropically consolidated to $300$ kPa, at which point it is NC$.$ Its critical$-$state friction angle is $18.$ The overall total stress on the sample is suddenly reduced by $140$ kPa; the sample is then sheared under undrained conditions, without any delay, in triaxial compression. Explain what happens to the sample, plotting total and effective stress Mohr$$s circles as needed. Draw the Mohr's circles please