The Colmix® process is one of four solutions that are part of the Deep Soil Mixing family. It involves using a single or multiple tool to build Soil Mixing columns. Use of this tool requires the power of a piling machine.

In the 1980s and 1990s, the Colmix® process referred to a method patented by Soletanche Bachy using several synchronised flight augers to build in-situ soil-cement columns. Cement was introduced during drilling and post-compactionof the mixture was done when the auger wasextracted.  The process was then almost exclusively used for soil improvement applications.

The process has evolved since then and now involves single or multiple augers to construct columns or groups of columns by mixing a cement grout with the soil in place.

This simplification has significantly expanded the range of soils that can be treated, as well as the potential range of applications.

For instance, the process has been used for hydraulic cut-off walls, structural applications (retaining structure, gravity walls and shafts) and even soil improvement (reinforcement of platforms, stabilisation of embankments, reinforcement of diaphragm wall abutments, load-bearing walls, anti-liquefaction treatments, etc.)

This solution is only employed as a wet process.

• Single Colmix® tool
  • Standard diameters: from 0.8m to 2.4m

• Multiple Colmix® tool
  • Standard diameters: from 2 x 0.80m to 2 x 1.5m
  • Standard diameters: 3 x 0.80m and 3 x 0.90m

What are the advantages of this technique?

Implementation

The single tool can be used on any pile machine of sufficient power. Multiple tools require machines equipped with a special rotating head.

During the drilling phase, the tool breaks down the structure of the in-situ soil. A cement grout is injected during this phase to facilitate the tool’s penetration and above all to incorporate the required quantity of binder to achieve the end properties of the mixed-soil column. Most of the mixing of the soil-cement material is therefore carried out during this phase. Mixing of the materials is refined during the auger extraction phase.

Intersecting columns are built according to the same principle, by drilling into pre-constructed columns (either fresh or once they have already started to set).

Did you know?

The Colmix® process was first used on a construction site to stabilise an embankment on the “Les Aubrais – Montauban” railway line in 1986.

Numerous projects have been carried out since then using the Colmix® process:

Processes other than Colmix® exist in the Deep Soil Mixing family of techniques:

• The Springsol® process
• The Trenchmix® process
• The Geomix® process