The European Federation for Specialist Construction Chemicals (EFNARC) has updated its 2001 mechanised tunnelling guidelines on the use of products for soft ground tunnelling at the same time as extending the advice to cover products for hard rock TBMs.
EFNARC involves a cross section of industry experts from manufacturers, researchers and users to write its reports. This approach means that as well as describing the current technology available, the guidelines also give practical advice.
The guidelines cover common requirements for TBMs; information on the use of speciality products for soft ground and hard ground conditions.
For soft ground, soil conditioners and slurry additives are considered. In terms of EPB machines, the guidelines cover foam, dispersing agents, anti-abrasion agents and additives that provide soil stabilisation or water retention. Stressing the use of the appropriate foam for the required soil conditioning, the guidelines propose the adoption of three classes of foam that are best applicable to different soil types from clays to sandy gravels.
The new section covering hard rock TBM applications focuses on the chemical products that have been developed to reduce clogging, abrasion and wear on the cutter head. Also addressed are dust control of the fine particles of material produced by the the TBM excavation.
Annulus grouts are considered, together with the various admixtures to adjust the properties of the grout such as retarders, accelerators, plasticisers and anti-shrink products.
EFNARC technical committees are currently working in the following areas: concrete repair; sprayed concrete; TBM tunnelling; flooring; fibres; self-compacting concrete; fire protection in tunnels and thin support liners. Further information is available on the federation’s website, www.efnarc.org , where the reports are freely downloadable and industry feedback is welcomed.
