Retaining & slopes · Anchors, nails & shoring
Shotcrete facing (soil nail / anchored wall) calculator
Flexure and punching-shear resistance of a reinforced shotcrete facing against the nail-head load, plus shotcrete volume with rebound.
Standard: FHWA GEC 7 (2015) facing flexure & punching · ASD
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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 |
|---|---|---|
| Facing | Temporary (initial) facing | |
| Shotcrete thickness h | 100 | mm |
| f'c | 28 | MPa |
| Mesh / bar fy | 500 | MPa |
| Mesh area at mid-span (each way) | 252 | mm²/m |
| Steel at nail head: mesh + waler bars | 452 | mm²/m |
| Nail spacing horizontal SH | 1.5 | m |
| Nail spacing vertical SV | 1.5 | m |
| Maximum nail design tension Tmax | 120 | kN |
| Bearing plate side | 200 | mm |
| Facing area (for quantities) | 300 | m² |
| Rebound & over-spray | 20 | % |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Unit moment, mid-span (mesh) | 5.97 | kNm/m |
| Unit moment, at nail head | 10.23 | kNm/m |
| Pressure factor CF | 2.00 | |
| Flexure resistance RFF | 259.1 | kN |
| Punching perimeter diameter D′c | 300 | mm |
| Punching resistance RFP | 164.6 | kN |
| Nail-head load To | 84.0 | kN |
| FS flexure | 3.08 | |
| FS punching | 1.96 | |
| Reinforcement ratio ρ (mesh) | 0.25 | % |
| Shotcrete volume incl. rebound | 36.0 | m³ |
- ✓ Flexure FS ≥ 1.35 — 3.08
- ✓ Punching FS ≥ 1.35 — 1.96
- ✓ Thickness ≥ 100 mm
- ✓ Steel at nail head ≥ mid-span mesh
Method, formulas and assumptions
- m = As·fy·(d − a/2), a = As·fy/(0.85 f′c b), d = h/2 = 50 mm
- CF = 2.0 (100 mm), 1.5 (150 mm), 1.0 (200 mm) for temporary facings; 1.0 permanent (GEC 7)
- RFF = CF (m,neg + m,pos) × 8·SH/SV (vertical) and × 8·SV/SH (horizontal); the smaller governs
- RFP = 0.33√f′c · π · D′c · h, D′c = bearing plate + h (punching cone, CP = 1.0)
- To = Tmax [0.6 + 0.2 (Smax − 1)] with Smax in metres (GEC 7)
- FS required: 1.35 temporary, 1.5 permanent (ASD)
- Permanent facings may also need headed studs; check them separately
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.