Two‑Mohr Circle Triaxial Calculator — φ and c from two tests

Two‑Mohr Circle Triaxial Calculator

Compute φ (deg), cohesion c (kPa), draw two Mohr circles & failure envelope, predict σ₁ for new σ₃

Input — Two consolidated drained triaxial tests

Test 1: σ₃ (kPa)

Test 1: σ₁ (kPa)

Test 2: σ₃ (kPa)

Test 2: σ₁ (kPa)

Predict σ₁ for new σ₃

σ₃ (kPa) to predict

 

Computation steps & formulas

We use the linearised triaxial failure relation: σ₁ = σ₃ · tan²(45° + φ/2) + 2c · tan(45° + φ/2)
Set Y = σ₁ and X = σ₃, then Y = mX + b where m = tan²(45° + φ/2) and b = 2c · tan(45° + φ/2). From two tests compute slope m, then extract φ and c.

Mohr diagram — σ (horizontal) vs τ (vertical)

Notes: Mohr circles are plotted for the two tests using centers (σ_avg,0) and radius (σ₁−σ₃)/2. The failure envelope τ = σ·tan(φ) + c is shown (in σ–τ space). Use different inputs to update the plot and results.

Detailed Step‑by‑Step Results