Temporary works & site · Platforms & excavations
Piling rig working platform (BRE 470) calculator
Granular working platform thickness for a tracked piling rig on a cohesive subgrade by the BRE 470 punching-shear method: track bearing pressure for the standing case (1) and the operating/extracting case (2), the subgrade capacity and the platform thickness that spreads the load. Section drawn to scale.
Standard: BRE 470 (2004) Working platforms for tracked plant · load cases 1 (γ = 1.6) and 2 (γ = 1.2) · cohesive subgrade
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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 |
|---|---|---|
| Track pressure, case 1 (standing/travelling) | 180 | kPa |
| Track pressure, case 2 (operating) | 260 | kPa |
| Track width | 0.9 | m |
| Track length | 5.2 | m |
| Platform friction angle φ' | 45 | ° |
| Platform unit weight | 20 | kN/m³ |
| Subgrade undrained strength cu | 35 | kPa |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Subgrade capacity cu·Nc·sc | 186 | kPa |
| Kp·tanδ | 5.83 | |
| Thickness required, case 1 | 0.89 | m |
| Thickness required, case 2 | 0.99 | m |
| Design thickness (≥ 0.3 m, rounded) | 1.00 | m |
- ✓ Platform thickness ≤ 2W (method valid) — 1.00 m
- ✓ Subgrade cu ≥ 20 kPa (else treat / geotextile) — 35 kPa
- ✓ Case 2 governs is noted — case 2
Method, formulas and assumptions
- BRE 470 cohesive subgrade: q·γ ≤ cu·Nc·sc + γp·D²·Kp·tanδ / W with sc = 1 + 0.2W/L, Nc = 5.14, δ = φ'. Load factors 1.6 (case 1) and 1.2 (case 2). Minimum 300 mm.
- Platform certificates, testing (plate load / DCP) and maintenance are required on site; consider geogrid reinforcement for weak subgrades.
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.