Temporary works & site · Platforms & excavations
Strutted trench: Peck apparent pressure & strut loads calculator
A braced trench with sheeting and struts at chosen levels: Peck's apparent pressure envelope (0.65KaγH for sand; soft or stiff clay forms), tributary strut loads by the hinge method and the maximum sheeting moment. Section drawn to scale.
Standard: Peck (1969) apparent earth-pressure diagrams · trench shoring practice
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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 |
|---|---|---|
| Trench depth | 5 | m |
| Trench width | 2.4 | m |
| Soil | Sand | |
| Sand φ' | 32 | ° |
| Clay cu | 50 | kPa |
| Unit weight | 18 | kN/m³ |
| Strut depths (m), comma separated | 0.6, 2.2, 3.8 | |
| Strut spacing along trench | 2 | m |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Apparent pressure (peak) | 18.0 | kPa |
| Strut at 0.6 m | 50 | kN |
| Strut at 2.2 m | 58 | kN |
| Strut at 3.8 m | 72 | kN |
| Max sheeting moment (≈ pL²/10) | 4.6 | kNm/m |
- ✓ Struts provided at ≤ 2 m vertical spacing — 1.60 m
- ✓ Soft clay basal heave check needed — n/a
Method, formulas and assumptions
- Peck apparent pressure envelopes: sand 0.65KaγH uniform; stiff clay 0.3γH trapezoid; soft clay γH(1 − 4cu/γH) ≥ 0.3γH. Strut loads by tributary heights (hinge at mid-way between struts); sheeting moment ≈ p·span²/10.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.