Deep soil mixing systems mix binder in situ with soft soils as ground improvement and mass soil stabilisation. The binder is typically cement, lime, blast furnace slag or a combination.

There are two main types of in situ dry soil mixing used in ground improvement:

• Mass Soil Mixing – Where a whole area of very soft or contaminated ground requires improvement. This system utilises an excavator with a soil mixing tool which mixes the material in the ground with either a dry binder or wet slurry which is introduced to stabilise the soil and raise the strength as required. Depths of 6 m can be achieved using this method.
  
• Deep Soil Mixed Columns – These may be single columns up to 23 m deep or overlapping triple columns installed up to 15 m in depth both with a piling rig type machine, for installation of foundations, ground improvement, cut-off walls or to improve the bearing capacity of the soil for example on embankments at risk of soil erosion.

In soils which are too deep for the mass soil mixing system we can utilise a combination of both ground improvement techniques where a series of soil mixed columns are installed with a mass soil mixed slab on top.

Traditionally buildings would be constructed in areas of good quality soils that could utilise simple foundation techniques but as more and more development takes place it is necessary to use land that is not initially suitable for building on. As a result ground is being developed containing soft soils such as alluvial silts, soft clays or even peat and ground improvement now plays a large part in any sizeable project.

Consideration of environmental issues and cost determine the type of ground improvement that may be used and in a bid to reduce the quantity of construction waste simply going to landfill a ground engineering solution that is being considered for use more and more is Deep Soil Mixing.

Contaminated ground is also being developed these days and whilst we are not principally a remediation contractor our equipment enables us to carry out soil or silt stabilisation which in turn is a remedial process utilised to bind or lock-in contaminates within the soil or silt matrix.
 
The major benefits of this treatment process are that the material can either be retained on site or disposed of to a suitable landfill site having met the pre-treatment criteria.

The processes we can provide are in-situ mixing with the contaminated material all being treated without the need to excavate. Hence no contaminates are being released into the air and becoming airborne. Mixing can be with lime, PFA and/or cement to modify the structure of the soil matrix. The additives react with water forming a physical bond which immobilises the contaminants through a pozzalanic reaction by changing the chemical constituents of the contaminates. The permeability of the treated material is reduced, thus inhibiting water movement and preventing leaching of the contaminates.

The moisture content of cohesive soils is also reduced, leading to a considerable improvement in bearing capacity. This technique is a cost effective alternative to importing aggregates for both temporary and permanent works.

Deep soil mixing is a technology that is widely used in Japan while countries throughout Europe including Germany and Scandinavia have been using it for over 25 years. Now it is available in the UK from Eco Foundations and is being utilised on a number of projects. Please see the latest projects section of our website to read our most recent case studies.

Soil mixed columns are also suitable for stabilising soft ground which is going to be used for pipelines. Please download our information sheet on soil mixing for pipeline installation for further details.

To learn more about the different types of soil mixing solutions we are able to offer please download our options for soil mixed foundations brochure and ground improvement by soil mixing brochure by clicking on the links.

Click on the link to view a video of the large diameter deep soil mixing process in action