Miglionico tunnel (Ferrandina – Matera La Martella railway line). Innovative solutions for rehabilitation works of tunnels in gassy rock masses and methane monitoring during the operational phase

Client: Italferr SpA
Project: Ferrandina – Matera La Martella new railway line – Miglionico tunnel
Date: 2018-19

Miglionico tunnel (Figure 1) is the most relevant work of the Ferrandina – Matera La Martella railway line, which will connect Matera to the Battipaglia – Potenza – Metaponto line.
The tunnel (6500 m long) was built during the ‘80s – ‘90s but never entered in operation due to structural damages, water and methane inflows occurred after completion. At the end of the ‘90s rehabilitation works were performed in the tunnel.
In 2018 Italferr started the design of rehabilitation and completion works. SERENGEO has been appointed to design innovative safety engineering solutions against detonation or deflagration of air – methane mixtures during:

  • Miglionico tunnel rehabilitation and modernization works (consolidation, demolition, final lining, etc.);
  • access tunnel’s excavation (Figure 1);
  • railway operational phase.

Figure 1 – Route of Miglionico line and access tunnels

Project goals

  • Evaluation of the hazard level associated with potential methane emissions and technical classification to be adopted during access tunnel’s excavation;
  • Develpoment of the safety measures and engineering solutions to be adopted, against air-methane mixtures’ detonation / explosion hazard, during tunneling works and railway operational phase.

Activities performed

  1. Bibliographic and hystorical documentation’s analysis on:
    • geo-structural framework and seismic events in the area surrounding the Miglionico tunnel’ route;
    • evidences of methane presence in the investigated area (Figure 2);
  2. Analysis and interpretation of methane investigations’ results (Figure 3);
  3. Critical analysis of excavation methods and techniques, section and technical data of the access tunnel;
  4. Definition of the methane emission model and technical classification of the access tunnel in relation to methane risk, according to “Grisù” Guideline;
  5. Development of the safety measures and procedures, against air – methane mixtures’ detonation / explosion hazard, to be adopted during:
    • access tunnel’s construction;
    • rehabilitation works of Miglionico tunnel;
  6. Study and design of an innovative automatic and continuous monitoring system (in the line and access tunnel) of the potential methane inflows into the tunnel during railway operations, with open and punctual IR detectors (Figures 4 and 5).

Innovative aspects

  • Design of a worldwide innovative automatic and continuous monitoring system of the potential methane inflows into the tunnel during railway operations.

Figure 2 – Route of the Miglionico line and access tunnels superimposed on the map of mining licenses for hydrocarbons exploration and exploitation (in force at March 31, 2019, source: UNMIG data, https://unmig.mise.gov.it/index.php/it/dati/ricerca-e-coltivation-di-idrocarburi)

Figure 3 – Miglionico tunnel: geo-structural profile and depth of the methane emissions detected in the geognostic boreholes before tunnel’s construction (a); methane volumetric concentrations measured during tunnel’s excavation (90’s) in consolidation holes (b) and during a supplementary survey campaign performed in 2004 – 05 (c)

Figure 4 – Sketch of methane diffusion inside the tunnel and of the innovative monitoring system with Open Path IR detectors: 1) emission from the reverse arc; 2) emission from the side facing.

Figure 5 – Elevation plot of the access tunnel (first figure) and arrangement of the IR detectors (red dots). Detail of the chamber and the filter area: longitudinal section (1) and cross sections of the chamber (a) and the filter area (b)