Small-diameter columns to improve the soil in-situ

Springsol® process can be applied in confined or limited headroom spaces to build soil-cement columns. This technique can be used for underpinning works as well.

Deep Soil Mixing/ confortement /amélioration de sol/reinforcing
Springsol® process (Deep Soil Mixing family)

Springsol® process is one of a wide range of solutions within the Deep Soil Mixing family. It uses a fixed or opening tool to construct columns using a small diameter drilling rig.


The process was initially developed in order to reinforce railway platforms without removing the tracks, while respecting certain requirements:

  • Work with low clearance (beneath overhead lines),

  • Drilling between railway sleepers,

  • Protection of ballast, particularly with regard to cementing,

  • Need for minimal traffic disruption.


Since then, the process has been applied to a wide variety of soil improvement works. As well as the reinforcement of railway platforms, the process was used for ground improvement works under paving, concrete slabs and footings, embankment stabilisation and in-situ soil remediation.


Like other soil-mixing elements, Springsol® columns behave as semi-rigid inclusions, stiffer than the non-treated soil, but softer and less rigid than concrete.


Depending on the presence of existing elements (paving, foundations, rocks, etc.), the soil is can be treated only at depth or directly from the surface. To do this, two types of tools can be used:


  • An opening tool
    • Folded diameter: 160mm or 225mm
    • Open diameter: 400mm/600mm or 800mm/900mm
    • Used for underpinning, and/or with limited headroom and/or in confined spaces.


  • A fixed tool:
    • Diameter: 400mm, 600mm, 800mm, 900mm
    • Used when working with limited headroom and/or in confined spaces.


Confortement/ amélioration de sol / reinforcing

What are the advantages of this technique?

Easy and versatile soil reinforcement technique

Minimum requirement in terms of equipment (small diameter drilling rig and compact grout production plant)

Limited risk of disruption (very low risk of settling or lifting)

No generation of vibrations

Guaranteed column dimensions

Limited emissions

Can be used with limited headroom and/or in confined spaces

Soletanche Bachy’s advantages

Soletanche Bachy’s advantages

  • A large fleet of equipment available, of all sizes and brands,
  • Proven experience in various countries around the world,
  • A patented process,
  • Recognised expertise in the field of cementitious grouts.



When using an opening tool, the Springsol® process includes five phases:

  • Preliminary installation of a casing (or preliminary coring),
  • Drilling with the tool, which opens once the bottom of the casing/coring has been reached,
  • Incorporation of grout at low pressure and mixing while drilling
  • Additional mixing while the tool is progressively extracted,
  • The tool folds up again for extraction via the casing/coring.


When used with a fixed tool, the Springsol® process simply involves low-pressure incorporation of grout and mixing during drilling, along with further mixing during extraction.

Implementation of the Springsol® process is accompanied by a supervision system to control the amounts of cementitious grout as well as the mixing quality. These specific quantities are recorded in real time, along with other execution parameters.

Samples are also taken of the fresh mixture during execution to ensure that the desired dimensioning parameters are met.

Execution controls and monitoring

Did you know?


  • Small diameter augers allow the columns to be constructed at any angle, from vertical to horizontal.
  • In some situations, the casing can be installed during the drilling phase with the opening tool.
  • This technique has also been patented for the installation of anchors, particularly in clay.



Here are a few of the projects carried out using the Springsol® process:

Station Orchard et ses tunnels associés (T219) - Singapour

T219 Orchard Station, Singapore (2018)

Completion of 600m3 of soil treatment using sub-horizontal Springsol® columns to minimise settlement during the excavation of a transfer corridor beneath the slab of the existing station.

The Deep Soil Mixing family of techniques also includes these processes in addition to Springsol®: