$2\mathrm{.}2.($a$)$ A specimen of cohesionless sand was tested in a triaxial compression test under a cell pressure of $100K\frac{N}{m^2}.$ If angle of internal friction for the sand is $45$ then find deviator stress at which the specimen will fail. $($b$)$ Define colomb;s strength envelop and sketch these for $c-$ soil, c$-$soil and $-$soil. $($CLO$-3/$PLO$-2$C$/C_2)$

$15+5$