Safety engineering in tunnelling with traditional technique through gassy rock masses and soils

Client: DIRPA 2 S.c.a.r.l.
Project: Road axis Marche – Umbria and district of internal penetration Maxilotto n. 2, Pedemontana delle Marche, tract “Fabriano – Muccia / Sfercia”
Date: 2016 in progress

The “Pedemontana delle Marche” project contemplates the excavation of several natural and artificial tunnels in potentially gassy rock masses and soils.
SERENGEO’s activity consists in technical – scientific assistance, during design and construction phases, on safety against detonation or deflagration of air – methane mixtures during the tunnels construction works.

GIS vision of the Pedemontana delle Marche

Serre tunnel’s face

Project Goals

  • Assessment of the likelihood that the excavation works can determine methane inflows towards the tunnels;
  • Specific guidance for safe design and construction of tunnels in gassy rock masses.

 Serre tunnel’s geological profile

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. Definition of an Integrative Methane Investigation Plan;
  3. Analysis of the methane investigation results and correlation with the geo-structural framework;
  4. Technical classification of tunnels in relation to methane risk, in application of the Marche Region’s Technical Note “Safety standards to apply during the realization of main infrastructural works: Underground works – Excavation in gassy soils” (Decree n.18/SPU, date: 06/09/2013);
  5. Definition of the technical measures and procedures to be used during tunnels construction to ensure the highest safety level against air / methane mixtures detonation and explosion;
  6. Technical support during construction phase, verification and update of the technical classification.

 Methane concentration (in % LEL) measured at borehole head during coring. The plot represents also the drilling depth versus time