The 'Mohr-Coulomb failure criterion' is plotted as:
Choose the correct answer
A parabolic curve in τ-σ space
Straight line in τ-σ space: τf = c + σ tanφ — Mohr circle tangent to failure envelope at failure
A vertical line at constant stress
Only used in elastic range
Correct Answer
B. Straight line in τ-σ space: τf = c + σ tanφ — Mohr circle tangent to failure envelope at failure
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Mohr-Coulomb: τf = c + σn tanφ. In τ-σ space: straight line with intercept c (cohesion) and slope tanφ (friction). Failure: when Mohr circle of stress is tangent to or touches this line. Principal stress form: σ1 = σ3 tan²(45+φ/2) + 2c tan(45+φ/2). Used for: retaining wall design, slope stability, bearing capacity, tunnel support. Simplest yet most widely used failure criterion in geotechnics.
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