Foundations · Pile testing & NDT
Thermal integrity profiling (TIP): effective diameter and cover calculator
Converts the average temperature at an anomaly to an effective radius, estimates cover to the cage and the cage offset from the spread between wires.
Standard: ASTM D7949 · temperature ∝ effective radius (linear model)
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 |
|---|---|---|
| Nominal diameter | 1 | m |
| Cage diameter (to thermal wires) | 0.75 | m |
| Soil (ambient) temperature | 22 | °C |
| Average temperature in sound shaft | 52 | °C |
| Average temperature at anomaly | 51 | °C |
| Hottest wire at anomaly | 52 | °C |
| Coolest wire at anomaly | 50 | °C |
| Specified minimum cover | 75 | mm |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Effective radius (D/2)(Ta − Ts)/(Tb − Ts) | 0.483 | m |
| Average cover re − dc/2 | 108.3 | mm |
| Radius per °C (D/2)/(Tb − Ts) | 16.67 | mm/°C |
| Cage offset ≈ k(Tmax − Tmin)/2 | 16.67 | mm |
| Cover on the tight side | 91.67 | mm |
| Check: De / D | 0.967 | |
| Effective diameter | 0.967 | m |
- ✓ Effective diameter ≥ 95 % of nominal
- ✓ Cover on the tight side ≥ specified
Method, formulas and assumptions
- Effective radius (D/2)(Ta − Ts)/(Tb − Ts) = 1/2*(51-22)/(52-22) = 0.48333 m
- Average cover re − dc/2 = (0.48333-0.75/2)*1000 = 108.33 mm
- Radius per °C (D/2)/(Tb − Ts) = 1/2/(52-22)*1000 = 16.667 mm/°C
- Cage offset ≈ k(Tmax − Tmin)/2 = 16.667*(52-50)/2 = 16.667 mm
- Cover on the tight side = 108.33-16.667 = 91.667 mm
- Check: De / D = 2*0.48333/1 = 0.96667
- Effective diameter = 2*0.48333 = 0.96667 m
- Linear temperature–radius model calibrated on the sound shaft; roll-off within about one diameter of the head and toe needs separate treatment.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.