ASSIGNMENT PROBLEM $2(5$ marks$)$

Three specimens $(1,2,3)$ from a completely decomposed granite $($CDG$)$ were tested in the laboratory

as reconstituted samples. These samples were composed of sand$-$size fractions having the same grain

size distribution. Direct shear tests were performed on these three specimens $($each tested at a different

normal stress, all of them tested at the same initial void ratio$)$ and the results in terms of peak and critical

state strength are summarized below:

Table $2\mathrm{.}1-$ Direct shear test results on specimens from the completely decomposed granite

Compute the angle of shear strength at peak and critical state $($i$.$e$.,$ compute separate friction angles for

the peak state and the critical state$)$ and show in graphs the failure envelopes $($you can print the graph

from excel file$).$ Indicate in the form of table a summary of your answer and explain your computations.

For your final answer, round the angles to the closest $0\mathrm{.}1$ degrees.

Additional information:

The shear box has a circular area with diameter of $60mm.$

Assume linear failure envelope using the Mohr$-$Coulomb failure criterion.