Soil Mixing Wall Calculator
Columns, mixed volume and cement for a three-axis mixing wall.
Quick answer
With the default inputs: Wall length 100 m · Wall depth 18 m · Column diameter 850 mm etc.Cement 556.0 t
Use your own dimensions ↓Inputs
Result
Cement
556.0t
| Spacing | 0.600m |
| Columns | 168bars |
| Mixed volume | 1716m³ |
| Cement ratio | 18% |
| Cement per metre of wall | 5.56t/m |
How this is worked out
SMW (Soil Mixing Wall) uses a three- or twin-axis mixer to blend cement grout with in-situ soil into a continuous wall that both retains and seals, often with H-beams inserted for strength. The cement ratio is cement weight ÷ natural soil weight; soft clay uses 15-20%, lower in sand, higher in silt. Natural density is taken as 1.8 t/m³, so cement = mixed volume × 1.8 × ratio. A triple-axis rig makes three columns per pass; spacing uses diameter − overlap and the overlap is not deducted, so the result is slightly conservative (safe side).
Next up: Soil Nail Wall Calculator · High Strength Bolt Torque Calculator
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Spacing | s = D − overlap |
| Columns | n = ⌈length/s⌉ + 1 |
| Mixed volume | V = n·πD²/4·depth |
| Cement | M = V·1.8·ratio% (t) |
100 m × 18 m, Φ850 triple-axis, 250 mm overlap, 18% ratio: 0.6 m spacing, ~168 columns, ~1716 m³ mixed, ~556 t cement, ~5.6 t per metre.
Cement by dosage ratio (100 m long, 18 m deep, 850 mm at 600 mm centres, from this page's formulas)
| Dosage | Total cement (t) | Per metre of wall (t/m) | Per m³ of mixed soil (kg/m³) | Note |
|---|---|---|---|---|
| 12% | 371 | 3.71 | 216 | Low end - granular soil, temporary works |
| 15% | 463 | 4.63 | 270 | Common lower bound |
| 18% | 556 | 5.56 | 324 | The usual value, and this tool's default |
| 20% | 618 | 6.18 | 360 | Common upper bound, tighter cut-off |
| 22% | 680 | 6.80 | 396 | Above the usual range - prove it with a trial panel |
Choosing a cut-off wall (qualitative; cost and depth vary by region and rig)
| Method | Cut-off reliability | Typical depth (m) | Footprint | Slurry / spoil | Where it fits |
|---|---|---|---|---|---|
| SMW mixing wall | Good, continuous | up to 25-30 | Small | Little spoil | Retaining plus cut-off, the workhorse |
| Jet grouting | Fair; joints between columns are the weak point | up to 30 | Small | Much return flow | Tight sites, local repair, spot cut-off |
| Secant pile wall | Very good, also retains | up to 30 | Small | Slurry | Deep, high-spec, close to buildings |
| Diaphragm wall | Best; can be the permanent structure | No practical limit | Large | Large slurry volume | Deep basements, high water table, city centres |
| Sheet piles + seal | Depends on the interlock; leaks | up to 15 | Small | None | Shallow or temporary works, recoverable |
Basis
- JGJ 79-2012 — cement-soil mixing chapter, including the cement ratio and curing requirements
- JGJ 120-2012 — use of mixing walls as a cut-off or as a gravity retaining structure
FAQ
How do I pick the cement ratio?
By soil and strength. Soft clay and silt need 15-20% to form a sound column; sand and silty sand can go down to 12-15%. The ratio sets both column strength and cut-off performance - too low and the column is loose and leaks. Use 18% for a first estimate; design comes from lab mix trials and a field test column, not a guess.
SMW vs jet grouting - what is the difference?
SMW mixes grout mechanically into the soil: uniform columns, lower cost, limited depth (generally ≤40 m). Jet grouting cuts and replaces soil with high-pressure grout, giving flexible diameter and depth where a mixer cannot reach, but at much higher cement use and cost. Pick SMW for regular long walls, jet grouting for spot strengthening and tight spaces.
What cement dosage should I use, and what happens if it is too low?
15-20% by mass of the in-situ soil is the usual band. Granular soils and temporary work take the low end; cohesive soils, tight cut-off and walls that also retain take the high end. Too little cement means strength does not develop and permeability does not drop, which shows up as weeping and bulging after excavation and, in the bad case, global instability. More is not better either: above roughly 22% the cement-soil shrinks more, cracks, and stops being watertight. On a new soil or a new mix, run a trial panel and core it for unconfined compressive strength.
Triple-axis or double-axis mixing - what is the difference?
Continuity and output. Triple-axis machines cut three columns per pass with a designed overlap between passes, which gives markedly better wall continuity and watertightness; it is the mainstream for SMW. Double-axis cuts two per pass, with smaller rigs and easier mobilisation, so it suits small jobs and restricted sites. Also check whether the auger can reach the design depth and how verticality is controlled - a leaning wall splits open at depth.
Does this tool check the wall's strength and stability?
No. It totals cement only - volume times soil density times dosage - which is a procurement figure. Strength, permeability, resistance to overturning and overall stability must be calculated by the designer to JGJ 79 / JGJ 120 using the ground investigation, and checked against strengths measured on cores from a trial panel. Reading cement content as a strength indicator is a common misuse: the same dosage in different soils can differ in strength by more than a factor of two.
How long until the mixed soil reaches strength, and how does that drive the programme?
Cement-soil gains strength far more slowly than concrete. The design value is normally quoted at 28 days, and excavation is usually held back at least that long, with some projects requiring a set fraction of the 28-day unconfined strength before digging. That fixes the programme: install the wall, cure, then excavate - the wait has to be in the schedule. Digging early to save time is the most common cause of bulging and weeping walls, and repairing it afterwards is very expensive.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Soil Mixing Wall Calculator. 2026-10-25. https://jianzhujisuan.com/en/soil-mixing-wall
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.