Foundations · Pile capacity
Driven pile capacity from SPT (Meyerhof) calculator
Shaft friction layer by layer from SPT N and base resistance from N at the toe with the embedment into the bearing layer (last row), then φg·Rug against the design action.
Standard: Meyerhof (1976): qb = 40N·Lb/D ≤ 400N kPa, fs = 2N̄ (displacement) or 1N̄ (small displacement) ≤ 100 kPa · AS 2159 φg
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 |
|---|---|---|
| Pile size (square side or diameter) | 0.4 | m |
| Section | Square | |
| Pile type | Displacement (precast, closed tube) | |
| Design action E* | 900 | kN |
| φg | 0.55 | |
| Layers from ground: thickness (m), average SPT N — last row is the bearing layer | 4, 3 5, 10 3, 18 4, 35 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Perimeter | 1.60 | m |
| Base area | 0.160 | m² |
| Shaft factor | 2.00 | kPa per N |
| Pile length | 16.00 | m |
| N at toe (bearing layer) | 35.00 | |
| Embedment in bearing layer | 4.00 | m |
| qb = min(40N·Lb/D, 400N) | 14,000 | kPa |
| Base resistance | 2,240 | kN |
| Shaft resistance | 819.2 | kN |
| Ultimate Rug | 3,059 | kN |
| Design φg·Rug | 1,683 | kN |
- ✓ φg·Rug ≥ E*
Method, formulas and assumptions
- Perimeter = IF(1=1,4*0.4,PI()*0.4) = 1.6 m
- Base area = IF(1=1,0.4^2,PI()*0.4^2/4) = 0.16 m²
- Shaft factor = IF(1=1,2,1) = 2 kPa per N
- Pile length = SUM([t.h]) = 16 m
- N at toe (bearing layer) = INDEX([t.N],COUNT([t.N])) = 35
- Embedment in bearing layer = INDEX([t.h],COUNT([t.h])) = 4 m
- qb = min(40N·Lb/D, 400N) = MIN(40*35*4/0.4,400*35) = 14000 kPa
- Base resistance = 14000*0.16 = 2240 kN
- Shaft resistance = SUM([t.Qs]) = 819.2 kN
- Ultimate Rug = 2240+819.2 = 3059.2 kN
- Design φg·Rug = 0.55*3059.2 = 1682.6 kN
- For cohesionless soils only; use the α-method for clay layers. AS 2159 φg depends on the average risk rating and testing (Cl 4.3).
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.