The additives and the polymers have been developed by CONDAT to cope with complicated geologies such as sticky, abrasive or very permeable ground.
In the most complicated cases:
- very abrasive rocks
- very sticky clay
- ground supersaturated with water...
the use of additives and polymers can provide effective treatment as a complement to the foam. These additives for foaming agents improve the productivity of tunnel boring machines.
In the case of clayey ground, sticking is a phenomenon that can reduce the speed of the tunnel boring machine and create clogging at the centre of the head or in the chamber. In parallel with the foam, it is possible to use an anti-sticking additive which is diluted online in the foaming solution.
For granular ground saturated in water, segregation between water and mud can occur. In this case, a polymer can be injected into the excavation chamber to correct the free water content and obtain homogeneous spoil.
CONDAT offers additives that can be used as a complement to the foam for ground treatment:
- Compared with treatment using conventional foam, TFA 42 allows for:
- reduction in the friction coefficient
- reduction in tool wear (effect validated by Penn State University, USA)
- The additive TFA 7 allows for:
- reduction in sticking and torque,
- easier excavation.
These 2 additives are completely compatible with the CLB F5 range and can be injected by means of a foam generator. CONDAT also offers polymers to be injected pure into the excavation chamber.
- For ground supersaturated in water or supersaturated in salt water, CONDAT offers TFA34 New Generation. These polymers bring:
- homogeneity to excavated spoil
- safe EPB operation
- In case of convergent surrounding grounds, TFA 34 injected pure through the ports of the shield and then diluted by the water allows for:
- reduce the thrust force on the jacks
- For hyperbaric interventions, injection of bentonite is generally used to form a cake. Addition of F11/M allows for:
- extended lifetime of the cake,
- increased resistance to pressure,
- protection against desiccation and reduction in loss of bentonite inside the ground.
|Supersaturation in water
|TFA 34 NewGeneration
|Supersaturation in salt water
|TFA 34 New Generation
|Unblocking the TBM