The T1 is a two-tube highway tunnel currently under construction near Constantine (Algeria) on the East-West Highway. Excavated using the conventional method in a complex limestone formation it is characterised by a cross section of about 200 square meters.
Tunnel construction by NATM started in 2010 and was then interrupted the 1st January 2014, when a great collapse involved the tube under construction and the one already finished, causing severe damages to final tunnel lining.
In order to solve this critical scenario SWS was appointed for the design and project management activities required for tunnels refurbishment and completion including: geotechnical, topographical and geophysical investigations, rock mass grouting from one of the existing tubes, pilot tunnel re-profiling, damaged lining demolition and reconstruction, as well as definition of a reliable monitoring plan.
SWS is facing several challenges in this project in all design phases. First, SWS developed a back-analysis based on 2D and 3D numerical models in order to understand what happened in the tunnel during the collapse. Then, a challenging theme has been the design, follow-up and continuous improvement by observational method of a complex system of injections. Finally, real-time monitoring of existing and freshly built structures, as well as the pillar between the twin tunnels and the whole rock mass above and around two tunnels.
SWS manages and integrates all data from investigations, monitoring and excavation 3D BIM model, continuously updated in real-time.