The Greek Railway Organization main railroad, to its northern exit from Athens, passes through a tunnel complex, consisting of four tunnels (two for each railway line), near the small city of Aghios Stefanos. The NE tunnel, approximately 200m long and 5m wide, was built from stones about 50 years ago. Due to suspected deformations of this tunnel in combination with known geological problems of the whole area, the Greek Railway Organizations ordered a stability check, along with a complete survey of the tunnel and the superjacent ground.
The cross-section based evaluation and comparison of the surveyed tunnel wall to its theoretical geometry revealed large deformations at specific locations (e.g. section 15). These locations have been defined and mapped in detail and repairing actions have been designed. Tunnel has been closed until repair works will be executed. Further geological investigation defined the reason of the deformations to be the presence of slate (sch) and clay (PT) formations at the tunnel’s area and the existence of a possible fault between them.