Temporary works & site · Piling works
Driven pile: Hiley formula (set, capacity, blows per 250 mm) calculator
Relates the final set per blow to the pile resistance for a drop or hydraulic hammer: R = ηh·W·h·ηb/(s + c/2), with the blow efficiency from the hammer and pile masses and the coefficient of restitution, and temporary compression from the cushion, pile and quake. Gives the set needed for a target resistance, the blows per 250 mm and the resistance at the observed set. Drawn to scale.
Standard: Hiley dynamic formula · AS 2159-2009 Cl 7.4 (dynamic formulae, φg) · temporary compression c = cc + cp + cq
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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 |
|---|---|---|
| Hammer ram mass | 7 | t |
| Drop height | 1 | m |
| Hammer efficiency ηh | 0.8 | |
| Pile size (square) | 400 | mm |
| Pile length | 18 | m |
| Coefficient of restitution | 0.4 | |
| Temporary compression: cushion | 4 | mm |
| Quake (ground) | 2.5 | mm |
| Target ultimate resistance | 2400 | kN |
| Observed set (last 10 blows / 10) | 4 | mm |
| Geotechnical reduction φg (dynamic formula) | 0.45 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Pile mass P | 7.06 | t |
| Blow efficiency ηb | 0.578 | |
| Energy delivered ηh·W·h·ηb | 31.8 | kJ |
| Set required for target R | 5.49 | mm/blow |
| Blows per 250 mm at target | 46 | |
| Resistance at observed set | 2,614 | kN |
| Design geotechnical strength φg·R | 1,177 | kN |
- ✓ Observed set ≤ required set (target reached) — 4.0 vs 5.49 mm
- ✓ Set ≥ 2 mm/blow (avoid overdriving / damage) — 5.49 mm
- ✓ Hammer/pile mass ratio ≥ 0.5 (drop hammer) — 0.99
Method, formulas and assumptions
- Hiley: R = ηh·W·g·h·ηb / (s + c/2), c = cc + cp + cq with cp = R·L/(A·E), E = 30 GPa. ηb = (W + e²P)/(W + P) when W > eP.
- AS 2159 limits φg for dynamic formulae (typically ≤ 0.45–0.50); calibrate with dynamic testing (PDA/CAPWAP) on a proportion of piles.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.