Safety Engineering in tunnelling with traditional technique and with EPB – TBM through gassy rock masses and soils

Client: Italferr SpA
Project: Palermo – Catania new railway line. Lots 1-2, 3, 4a, 4b and 5
Date: 2019-20

The Palermo – Catania new railway line project (Lots 1 – 5) (Figure 1) involves the excavation of more than 134 km of line and service tunnels (access and pedestrian tunnels) in potentially gassy rock masses and soils.
SERENGEO provided in technical – scientific assistance, during definitive design, on safety against detonation or deflagration of air–methane mixtures during tunnels’ construction works.

Route of the Palermo – Catania existing and new railway lines

Project goals

  • Evaluation of the hazard level associated with potential methane emissions during tunnels’ construction and technical classification of 17 line tunnels and 8 service tunnels (access and pedestrian tunnels);
  • Specific guidance for safe design and construction of tunnels (with traditional excavation technique and EPB-TBM) in gassy rock masses and soils.

Activities performed

  1. Bibliographic and hystorical documentation’s analysis on:
    • geo-structural framework and seismic events in the area surrounding the Palermo – Catania new railway line’ s route;
    • evidences of methane presence in the investigated area;
  2. Definition of the technical specifications for methane investigations in the formations interested by construction works;
  3. Analysis and interpretation of methane investigations’ results;
  4. Critical analysis of excavation methods and techniques, section and technical data of the line and service tunnels;
  5. Definition of the methane emission model and technical classification of the line and service tunnels in relation to methane risk, according to “Grisù” Guideline;
  6. Definition of the criteria and technical specifications for the EPB-TBM design and construction for tunnelling in gassy formations, according to “Grisù-TBM” Guideline;
  7. Development of the safety measures and procedures, against air–methane mixtures’ detonation / explosion hazard, to be adopted during line and service tunnels construction to ensure the highest safety level.

Palermo – Catania new railway line’s route and explotation and production wells drilled between the early 1900s and 2016, in which methane was detected (UNMIG data, VIDEPI project, .asp)

Geo-structural profile and depth of methane emissions detected in the boreholes along the Dittaino tunnel’s route (Lot 4b)