Unconfined compression test calculator

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Worked example — results

• ✓ L/D between 2 and 2.5
• ✓ Peak reached before 20 % strain

Method, formulas and assumptions

• Corrected area A = A0/(1 − ε)
• σ = P / A
• su = qu/2
• E50 = (qu/2)/ε50

Related site investigation calculators

• Oedometer consolidation test — Lab sheet: e–log σ' curve, Cc, Cr, Casagrande preconsolidation pressure, mv per stage and cv by Taylor's…
• Triaxial test (UU / CU / CD) — Mohr circles and failure envelope from triaxial specimens: su for UU, c′ and φ′ for CU (with pore pressure)…
• Direct shear test — Peak (and residual) failure envelopes from shear box results.
• Permeability (constant / falling head) — Hydraulic conductivity from constant- or falling-head tests, corrected to 20 °C.
• Stress paths (MIT p′–q) and strength fit — Total and effective stress paths from triaxial data, with the Kf line fitted to give c′ and φ′.
• Coefficient of consolidation (root-time & log-time) — cv from Taylor's t90 and Casagrande's t50, with permeability from k = cv·mv·γw.
• Collapse potential (oedometer) — Collapse potential from the strain on wetting at constant stress, with the usual severity classes.
• Free swell & swell pressure (oedometer) — Free swell strain under seating load and swell pressure from the constant-volume or load-back method.
• Residual strength: ring shear — Residual friction angle from a regression through the origin and a free-intercept fit.
• Vane shear (lab / field) — Undrained strength from peak and remoulded torque, sensitivity and Bjerrum's plasticity correction.