Maintenance Robotics in TBM Tunnelling

Among the various domains of the construction sector, tunnelling exhibits its own specificities in particular in terms of risks. Several techniques have been developed through the years in order to make excavation works more efficient and safer. Tunnel Boring Machines (TBM) were invented some 60 years ago and the concept since went through several significant improvements that have nowadays made them the preferred approach for the vast majority of tunnel projects, whether in hard rock or in soft ground. In TBMs a rotating cutter head carries excavation tools that are submitted to wear, which can be intense in hard and abrasive grounds. Replacing these excavation tools is a difficult operation especially in pressurised TBMs, in which two main problems appear: operator health and safety due to repeated compression and decompression cycles; slow overall interventions reducing the overall TBM efficiency. In addition, working close to a potentially unstable excavation front is inherently risky; handling devices weighing close to 200 kg is also a source of accidents and skeletomuscular trauma. Through the EC-funded NeTTUN project we intend to solve the above three problems, by developing a specialised maintenance robot. This system will handle the whole cycle of excavation tools replacement on a TBM. This paper goes through the currently implemented maintenance operations with a focus on pressurised machines, the possible alternatives, and describes the NeTTUN robotic system under development. It explains the general concept and rationale behind the technical choices made, states the targeted performance, and gives some insight on its detailed design.