Jonian Highway S.S. 106 – DG41/08, Mega lot 3. Tunnelling through gassy rock masses. Technical – scientific advisory support during desing and construction phases

Client: Sirjo S.C.p.A.
Project: Jonian Highway S.S. 106 – DG41/08. Mega lot 3
Date: January 2022- October 2024

The “Jonian Highway S.S. 106 – DG41/08, Mega lot 3” project (Figure 1) contemplates the excavation of natural and artificial tunnels in potentially gassy rock masses.
SERENGEO provided technical – scientific advisory support, during design and construction phases, on safety against detonation or deflagration of air – methane mixtures during construction works of “Trebisacce” and “Roseto 1” tunnels and of Trebisacce adit.

Figure 1. Jonian Highway S.S. 106 – DG41 route: tunnels are located in the Northern section (“Tratto 2”)

Project goals

  • Assessment of the likelihood that the excavation works can determine methane inflows towards the tunnels during the construction works and technical classification of Trebisacce adit;
  • Technical – scientific guidance for safe design and construction of tunnels in gassy rock masses.

Activities performed

  1. Bibliographic and documental analysis in order to evaluate the potential presence of methane in the rock masses interested by Trebisacce tunnel’s excavation;
  2. Analysis and interpretation of methane investigations’ results (Figures 2 and 3);
  3. Definition of the hypotetical methane emission model and technical classification of Trebisacce adit in relation to firedamp risk, according to “Grisù” Guideline;
  4. Definition of the technical measures and procedures to be used during tunnels and adit’s construction to ensure the highest safety level against air – methane mixtures detonation / deflagration;
  5. Technical support, validation and update of the technical classification during construction.

Figure 2. Trebisacce tunnel: boreholes in which methane concentration measurements with “Gas trap” technique were performed. The boreholes are marked with different colors depending on measurement results (red circles: methane detected / green circles: methane not detected).

 

Figure 3. Methane emissions (green circles) recorded during boreholes drilling along Trebisacce tunnel route: black line, CH4 measurements performed; blue line, CH4 measurements not performed. The boreholes where methane was detected are marked in red.