Question

The equation for the unconsolidated un drainage strength of clay is __________

(a) τ = c + σ tan φ

(b) τf = ccu + σ tan φcu

(c) τ = c + σ

(d) τ = σ tan φ

The question was posed to me during an interview.

My question is taken from Shear Strength of Cohesive Soil topic in chapter Shear Strength of Geotechnical Engineering I

Answer 1

Right option is (b) τf = ccu + σ tan φcu

The explanation: The equation for consolidated undrained strength of the preconsolidated clay in terms of total stress can be approximately expressed as τf = ccu + σ tan φcu where, σ is the normal pressure.