Retaining & slopes · Anchors, nails & shoring
Soil nail wall (simplified) calculator
Nail forces from active pressure, pull-out beyond the failure plane and tendon tension for each nail row.
Standard: FHWA GEC 7 concepts · Rankine active wedge
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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 |
|---|---|---|
| Wall height | 6 | m |
| Vertical spacing | 1.5 | m |
| Horizontal spacing | 1.5 | m |
| Nail length | 6 | m |
| Drill hole diameter | 0.1 | m |
| Ultimate bond strength | 100 | kPa |
| Bar diameter | 25 | mm |
| Bar fy | 500 | MPa |
| Soil γ | 19 | kN/m³ |
| Soil φ′ | 30 | ° |
| Surcharge | 10 | kPa |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Ka | 0.333 | |
| Bar area | 491 | mm² |
| Min pull-out FS | 2.12 | |
| Min tendon FS | 2.98 | |
| Row at 0.75 m: T, Lp, R | 18 kN, 2.97 m, 93 kN | |
| Row at 2.25 m: T, Lp, R | 40 kN, 3.83 m, 120 kN | |
| Row at 3.75 m: T, Lp, R | 61 kN, 4.70 m, 148 kN | |
| Row at 5.25 m: T, Lp, R | 82 kN, 5.57 m, 175 kN |
- ✓ Pull-out FS ≥ 2.0
- ✓ Tendon FS ≥ 1.8
Method, formulas and assumptions
- T = Ka(γz + q)·Sh·Sv (simplified apparent pressure)
- Failure plane at 45 + φ/2 from the toe; Lp = L − La
- Pull-out R = π·Dd·qs·Lp; tendon = As·fy
- Global and compound stability must be checked separately (slope tool / software)
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.