Site investigation · Laboratory: strength & consolidation
Pocket penetrometer & consistency calculator
Converts pocket penetrometer readings (≈ qu) to su and the AS 1726 consistency term.
Standard: AS 1726 consistency terms
Open the live calculator → All site investigation calculators
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Readings: depth (m), qu (kPa) | 0.5, 180 1.0, 220 1.5, 260 2.0, 300 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Mean su | 120.0 | kPa |
| Lowest su | 90.00 | kPa |
- ✓ All readings stiff or better (su ≥ 50)
Method, formulas and assumptions
- Mean su = AVERAGE([t.su]) = 120 kPa
- Lowest su = MIN([t.su]) = 90 kPa
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)…
- Unconfined compression test — Stress–strain with area correction, peak qu, su = qu/2 and E50 secant modulus.
- 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.
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.