Innovative safety engineering solutions for double shield TBM tunnelling in rock masses containing methane, hydrogen sulfide and other hazardous gases

Client: Salini Impregilo SpA – Strabag SE
Project: Brenner Base tunnel – “Mules 2–3” Lot
Date: 2015

The “Mules 2 – 3” Lot’s project contemplates the realization of an exploratory tunnel (12,5 km) and two one-track parallel tunnels (about 16 km each) of the Brenner Base Tunnel, in the stretch between the Mules window and the Northern national border.
Preliminary investigations along the tunnel path highlighted the presence of methane in the formations interested by tunnels tracks.
SERENGEO’s activity consisted, during tender phase, in developing technical and technological solutions to guarantee the maximum safety level during tunnels excavation with double shield TBM through rock masses containing methane, hydrogen sulfide and other potentially explosive gases.

Portion of the exploratory tunnel’s geological profile (not in scale). Areas where H2S and CH4 are expected (with orange line level 1, in blue line level 2)

Project Goals

  • TBM’s design for tunnel excavation through potentially gassy rock masses;
  • Ventilation system’s design to prevent the risk of air – methane mixtures and other potentially explosive gases’ detonation / explosion.

 TBM’s ventilation schemes

Innovative aspects

Study of innovative technical solutions for tunnelling with double shield TBM in rock masses containing methane, hydrogen sulfide and other potentially hazardous gases.

Activities performed

  1. Analysis of the state of art (causes of accidents occurred during tunnelling with TBM in gassy rock masses , best practices and successful technological solutions);
  2. Analysis of the investigations carried out for methane gas search;
  3. Assessment of the likehood that tunnel excavation can induce methane inflows into the underground site;
  4. Definition of the technical solutions to be adopted for methane and other potentially hazardous gases risk mitigation during the tunnel excavation with double shield TBM.