While recognizing that you need at least three direct shear tests to

draw a Mohr$-$Coulomb failure envelope, you attempt to estimate the

equation of the failure envelope through one test. You consolidate a dry

sand sample under a vertical pressure of $2142$ psf and the shear stress

at failure is $1627$ psf$.$ If you are able to estimate the equation of the

failure envelope, do so$.$ If you are unable, explain why.

While recognizing that you need at least three direct shear tests to

draw a Mohr$-$Coulomb failure envelope, you attempt to estimate the

equation of the failure envelope through one test. You consolidate a

saturated sandy clay sample under a vertical pressure of $4099$ psf and

the shear stress at failure is $3586$ psf$.$ If you are able to estimate the

equation of the failure envelope, do so$.$ If you are unable, explain why.