Foundations · Pile capacity
Pile capacity and settlement from CPT (LCPC method) calculator
Pile designed directly from a cone penetration test, as in the GEO5 Pile CPT program. The equivalent base resistance qca is the mean qc within 1.5D above and below the toe, clipped to 0.7–1.3 times that mean; qb = kc·qca. Shaft friction in each reading is qc/α limited by the LCPC maximum for clay/silt or sand/gravel and bored or driven piles. The design capacity uses φg, and the settlement at the working load uses the Randolph–Wroth stiffness with soil modulus from qc.
Standard: Bustamante & Gianeselli (1982) LCPC method · AS 2159-2009 φg · Randolph & Wroth (1978) head stiffness with E = αE·qc
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 |
|---|---|---|
| CPT: depth (m), qc (MPa), soil (1 = clay/silt, 2 = sand/gravel) | 0.5, 0.85, 1 1.0, 0.90, 1 1.5, 0.95, 1 2.0, 1.00, 1 2.5, 1.05, 1 3.0, 1.10, 1 3.5, 1.15, 1 4.0, 1.60, 1 4.5, 1.68, 1 5.0, 1.75, 1 5.5, 1.83, 1 6.0, 1.90, 1 6.5, 1.98, 1 7.0, 2.05, 1 7.5, 2.13, 1 8.0, 2.20, 1 8.5, 2.27, 1 9.0, 2.35, 1 9.5, 2.42, 1 10.0, 2.50, 1 10.5, 2.58, 1 11.0, 2.65, 1 11.5, 2.73, 1 12.0, 9.00, 2 12.5, 9.40, 2 13.0, 9.80, 2 13.5, 10.20, 2 14.0, 10.60, 2 14.5, 11.00, 2 15.0, 11.40, 2 15.5, 11.80, 2 16.0, 12.20, 2 16.5, 12.60, 2 17.0, 13.00, 2 17.5, 13.40, 2 18.0, 13.80, 2 18.5, 14.20, 2 19.0, 14.60, 2 19.5, 15.00, 2 20.0, 15.40, 2 | |
| Pile type | Bored / CFA (LCPC category I) | |
| Diameter | 0.6 | m |
| Length (toe depth) | 16 | m |
| Geotechnical reduction φg | 0.5 | |
| Design load N* | 800 | kN |
| Working (serviceability) load | 600 | kN |
| Pile modulus | 30000 | MPa |
| Soil modulus factor E = αE·qc | 3 | |
| Soil Poisson's ratio | 0.3 | |
| Allowable settlement | 15 | mm |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Mean qc within ±1.5D of the toe | 12.20 | MPa |
| Equivalent qca (clipped 0.7–1.3) | 12.20 | MPa |
| Base factor kc | 0.15 | |
| Base resistance qb / Rb | 1,830 kPa / 517 kN | |
| Shaft resistance Rs | 1,252 | kN |
| Ultimate capacity Rug | 1,769 | kN |
| Design capacity φg·Rug | 885 | kN |
| Average shaft modulus / base modulus | 12.8 / 36.6 | MPa |
| Head stiffness (Randolph–Wroth) | 121 | MN/m |
| Settlement at the working load | 4.9 | mm |
- ✓ N* ≤ φg·Rug — 90 %
- ✓ Settlement ≤ allowable — 4.9 mm
- ✓ CPT extends ≥ 1.5D below the toe
Method, formulas and assumptions
- LCPC: qca = mean of qc within a = 1.5D above and below the toe after discarding values outside 0.7–1.3 of the raw mean; qb = kc·qca with kc = 0.375 (clay/silt) or 0.15 (sand/gravel) for this pile type.
- Shaft friction per reading fs = qc/α ≤ fmax with α and fmax from simplified LCPC categories (bored); integrate fs·πD over the shaft.
- Settlement: Randolph & Wroth with G = E/2(1 + ν), E = αE·qc averaged over the shaft (αE ≈ 2–4 sand, 3–6 clay).
- Values are indicative; calibrate α and kc with static load tests (AS 2159 Sec 8).
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.