# Soil Mixing Wall Calculator Columns, mixed volume and cement for a three-axis mixing wall. - Page: https://jianzhujisuan.com/en/soil-mixing-wall - Category: Construction (https://jianzhujisuan.com/en/c/construction) - Chinese version: https://jianzhujisuan.com/zh/soil-mixing-wall.md - Data checked: 2026-10-25 ## Quick result With the default inputs (Wall length 100 m, Wall depth 18 m, Column diameter 850 mm (triple-axis), Overlap 250 mm, Cement ratio 18%): **Cement 556.0 t** ## Inputs | Parameter | Type | Default | Unit | Note | |---|---|---|---|---| | Wall length | number | 100 | m | | | Wall depth | number | 18 | m | | | Column diameter | select | 850 mm (triple-axis) | — | | | Overlap | number | 250 | mm | Overlap between adjacent columns | | Cement ratio | number | 18 | % | Cement as % of natural soil weight, 15-20% in soft clay | ## Formula - **Spacing**: s = D − overlap - **Columns**: n = ⌈length/s⌉ + 1 - **Mixed volume**: V = n·πD²/4·depth - **Cement**: M = V·1.8·ratio% (t) ## Worked example 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 | ## Questions ### 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. ## Related tools - [Plaster and Render Calculator](https://jianzhujisuan.com/en/plaster-coat): Mortar, cement and sand by layer for internal plastering. - [Mortar Mix Design Calculator](https://jianzhujisuan.com/en/mortar-strength): Trial strength, cement, water and sand, and the mix by mass. - [Labour Days and Crew Calculator](https://jianzhujisuan.com/en/labor-productivity): Man-days, crew size and labour cost from output rates. - [Line-of-Balance Duration Calculator](https://jianzhujisuan.com/en/schedule-flow): Rhythmic flow duration with overlap and break adjustments. - [Material Storage Area Calculator](https://jianzhujisuan.com/en/material-storage): Net footprint, total area and a suggested bay size. - [Dewatering Calculator](https://jianzhujisuan.com/en/dewatering): Pit inflow by the equivalent-well method, then well count. --- Generated by BuildCalc. All calculations run in your browser; no data is uploaded. Formulas follow national standards and common trade practice; local codes govern.