Foundations · Pile testing & NDT
Static pile load test interpretation calculator
Load–settlement readings: Davisson offset limit load, 10 % of diameter criterion and Chin's hyperbolic ultimate, then the design capacity from the governing value.
Standard: ASTM D1143 · AS 2159-2009 Section 8 · Davisson (1972) · Chin (1970) · 10 % D
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 diameter D | 0.6 | m |
| Pile length L | 18 | m |
| Pile modulus E | 32 | GPa |
| Design action E* | 1200 | kN |
| Geotechnical reduction φg (with static testing) | 0.75 | |
| Readings: load Q (kN), head settlement s (mm) | 0, 0 400, 0.99 800, 2.22 1200, 3.81 1600, 5.93 2000, 8.89 2400, 13.33 2800, 20.74 3200, 35.56 3400, 50.37 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Area πD²/4 | 0.283 | m² |
| Elastic compression per kN L/(AE) | 0.002 | mm/kN |
| Davisson offset 4 + D/120 | 9.00 | mm |
| 10 % D | 60.00 | mm |
| Davisson limit load | 2,427 | kN |
| Load at 10 % D | 0.000 | kN |
| Chin slope of s/Q vs s | 0.000 | 1/kN |
| Chin ultimate 1/slope | 4,000 | kN |
| Maximum test load | 3,400 | kN |
| Ultimate for design: Davisson if reached, else max test load | 2,427 | kN |
| Design capacity φg·Rug | 1,820 | kN |
- ✓ φg·Rug ≥ E*
- ✓ Test taken past the Davisson line
Method, formulas and assumptions
- Area πD²/4 = PI()*0.6^2/4 = 0.28274 m²
- Elastic compression per kN L/(AE) = 18/(0.28274*32*1000) = 0.0019894 mm/kN
- Davisson offset 4 + D/120 = 4+0.6*1000/120 = 9 mm
- 10 % D = 0.6*100 = 60 mm
- Davisson limit load = MAX([t.Qx]) = 2426.9 kN
- Load at 10 % D = MAX([t.Q10]) = 0 kN
- Chin slope of s/Q vs s = SLOPE([t.yy],[t.xx]) = 2.500e-4 1/kN
- Chin ultimate 1/slope = 1/2.500e-4 = 3999.9 kN
- Maximum test load = MAX([t.Q]) = 3400 kN
- Ultimate for design: Davisson if reached, else max test load = IF(2426.9>0,2426.9,3400) = 2426.9 kN
- Design capacity φg·Rug = 0.75*2426.9 = 1820.2 kN
- Chin's value is an extrapolation and usually over-predicts; it is reported for comparison, not used for design.
- AS 2159 also requires the serviceability (settlement) performance at working load to be checked.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.