Safety Engineering solutions for small section tunnels excavation with EPB-TBM in gassy rock masses

Client: Caposele s.c.a.r.l.
Project: Completion works of Sele-Calore Aqueduct tunnel alternative to Pavoncelli tunnel, aka Pavoncelli bis, Caposele (AV, Italy)
Date: 2016-17

Pavoncelli bis tunnel was designed as an alternative to the existing Pavoncelli tunnel, that since its construction in the early ‘900s was subject to disruption phenomena, increased by the 1980 Irpinia’s earthquake.
Tunnelling works crossed relevant structural discontinuities (faults and folds, fractured rock masses, etc.), which allowed for continuous and massive methane flows from the surrounding rock mass toward the tunnel.
SERENGEO provided technical-scientific assistance during Pavoncelli bis construction phase, studying the safety engineering aspects of small section EPB-TBM tunnelling in gassy rock masses.

Location and track of the Pavoncelli bis tunnel

Project Goals

  • Assess the effectiveness of the technical and technological solutions adopted for safe excavation, with TBM – EPB, of small section tunnels in potentially gassy rock masses;
  • Technical classification of tunnel in relation to methane risk, during the realization of construction works for unlocking the TBM, stopped by instability phenomena while crossing a fault;
  • Assess potential methane gas inflows towards the tunnel during construction works beyond the point where TBM was blocked (between km 6+170 and 8+510)

Activities performed

  1. Bibliographic and documental analysis in order to evaluate the potential presence of methane in the rock masses interested by the construction works;
  2. Technical classification, in relation to methane risk, of the small tunnel designed to unlock the TBM;
  3. Review of the technical and technological design solutions adopted by the Client to prevent the coexistence of ignition sources and potentialliy explosive methane–air mistures within the tunnel;
  4. Technical classification, in relation to methane risk, of the remaining tunnel track with traditional technique, as an alternative to TBM tunnelling.
Original solutions designed and implemented on the EPB-TBM for firedam risk prevention
Geological – structural profile and methane emission recorded along Pavoncelli bis track