Soldier Pile Calculator
Pile count, concrete and reinforcement - with jet-grout cut-off, a full retaining line.
Also known as soldier pile wall · king post wall · soldier beam
With the default inputs: Wall length 60 m · Pile diameter 800 mm · Pile length 18 m etc.Number of piles 51 bars
Use your own dimensions ↓Inputs
Result
| Actual spacing | 1.20m |
| Volume per pile | 9.0m³ |
| Total concrete | 461.4m³ |
| Reinforcement | 41529kg |
| Tonnes | 41.5t |
How this is worked out
This page is a quantity take-off only. It contains no code limits and no design - embedment depth, internal forces and reinforcement have to be worked out to JGJ 120-2012 separately. Piles sit on a centre spacing, count = ⌊length ÷ spacing⌋ + 1 with a pile at each end, then back-calculate the actual spacing. A soldier-pile line needs a cut-off between piles - jet grout, deep mixing or interlocking piles - or water and fines bleed through the gaps. The 90 kg/m³ reinforcement is an experience range for retaining piles (main bars + spiral + stiffeners), not a code value; use the placing drawing for a firm number. A capping beam ties the row together and is not included here.
Next up: High Strength Bolt Torque Calculator · Plaster and Render Calculator
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Pile count | n = ⌊length ÷ spacing⌋ + 1 |
| Per pile | V₁ = π×(d/2)² × length |
| Concrete | V = n × V₁ |
| Reinforcement | ≈ concrete × 90 kg/m³ |
How to work it out
- Piles = ⌈retention length ÷ spacing⌉, spacing usually 1.5-2.5× the diameter (typically 1.2-2.0 m).
- Concrete = piles × π/4 × D² × length; length must satisfy embedment depth, not just reach the pit bottom.
- Reinforcement is about 90 kg/m³; a soldier pile works in bending, so main bars go on the tension side.
- The capping beam must be continuous, tying the row into a single unit that acts together.
- Seal between piles with interlocking jet-grout or mixing columns, or a shotcrete facing over mesh, to stop soil loss.
Where it goes wrong
- Spacing too wide - soil flows out between piles and the wall caves in; the retention is a sham.
- Piles too short, embedment insufficient - soil is squeezed out below the pit floor and the wall kicks or overturns; the most dangerous pit failure.
- Discontinuous capping beam, unlinked pile heads - individual piles act alone with far less stiffness, large movement, and instability.
Material and cost
Bored soldier piles run mid-range all-in (piles + capping beam + inter-pile seal), cheaper than a diaphragm wall, and are the mainstream retention for medium-depth pits. Diameter, spacing and embedment drive the cost - optimise these three and you save money.
On site
- Keep the capping beam continuous with adequate section and steel - it is the key to unity.
- Seal between piles promptly to stop water and soil being drawn out from behind.
- Monitor pile-head and deep horizontal displacement; add struts the moment limits are exceeded.
Basis
- CIRIA C760 Guidance on embedded retaining wall design (soldier pile and lagging)
- EN 1997-1:2004, Section 9 (retaining structures)
- BS 8004:2015, Section 7 and 9 (piling and retention)
- FHWA-NHI-14-007 Ground Anchors and Anchored Systems (US practice)
FAQ
How wide can soldier pile spacing be?
How is pile length set?
What to calculate next
These jobs are done back to back on site — follow the steps to work through the whole sequence.
Retaining: pressure to supportStep 3 of 4
- 1Earth Pressure Calculator
- 2Retaining Wall Stability Calculator
- 3Soldier Pile Calculator
- 4Ground Anchor Calculator
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Soldier Pile Calculator. 2026-10-25. https://jianzhujisuan.com/en/soldier-pile