Project Description
Soil consolidation by biocalcification
Soletanche Bachy is developing Biocalcis®– a biotechnology capable of copying a natural phenomenon – for its worksites.
What is Biocalcis® ?
This innovative biotechnology emulates natural calcification processes to cement soil in situ while maintaining its initial porosity. A number of bacteria present in the natural environment are known to precipitate a variety of calcium carbonate minerals that build up over centuries to form calcareous concretions with excellent mechanical properties.
Sporosarcina pasteurii bacteria are non-pathogenic and environmentally harmless. They are cultivated using an industrial protocol developed by Soletanche Bachy. Calcite precipitation achieved by causing the bacteria to react with a calcifying nutrient solution.
Mains characteristics of the process
The bacteria – a few microns in length – are small enough to be injected into fine-grained soils K<10-5 m/s
The viscosity of the bacterial suspension and the calcifying solution is close to that of water
No pressure increases during injection
Rapid reaction time: final mechanical strength is obtained within a few hours
Pores remain open after treatment – permeability does not change
Range of UCS values possible, from 0.1 MPa to several MPa
The application scopes covered by this process :
- Restoration of reinforced soil retaining walls
- Mitigation of soil liquefaction
- Treatment to prevent internal erosion of embankments and slopes
- Deepening of quay walls
- Stiffening of soils under structures sensitive to vibrations
- Artwork of stone & historical monuments restoration
The advantages of this technique
Possibility of implementation into non-injectable fine soils, in which cement or chemical grouts could not be used
Implementation using conventional injection methods (Tube à Manchette – Slotted pipes)
Use of soil in situ
Increase in the mechanical resistance of soils and their cohesion without any significant impact on their initial permeability
Much lower carbon footprint than conventional cement-based solutions
Biocalcis® implementation
Inject in successive phases:
- Inject bacteria
- Wait several hours to fix the bacteria in the soil
- Inject the calcifying solution (urea/CaCl2)
- Exposure time required for biocalcification (several hours)
- Final flush
The calcifying solution injection cycle can be repeated several times depending on the desired level of biocalcification.
Why work with Soletanche Bachy?
Complete control over dimensioning and treatment protocol
A numerical model developed by our design office specifically for Biocalcis®
Completion of numerous tests in real-life situations and in-situ applications (retaining wall, dykes, underpass, embankment, etc.)
Execution controls and monitoring
Various actions can be carried out to validate the Biocalcis® solution:
- Column injection tests in the laboratory with material taken from the site to check the feasibility of the treatment and its mechanical performance,
- Suitability tests in the field to confirm the final dimensioning of future work,
- Soil Investigation campaign with core drilling and penetrometer tests to check the quality of the final result,
- Geophysical monitoring.
Did you know?
The Biocalcis® process may be used as an alternative to injection treatments in soils that are difficult to inject with conventional grouts. It can also be a good alternative to jet grouting or other techniques used for anti-liquefaction applications. It is a non-intrusive and environmentally-friendly solution.
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