ABSTRACT
Due to its old age and to the lack of detailed construction data, before proceeding with the tunnel enlargement it is necessary to characterise as well as possible the structure. First of all it has been necessary to evaluate the tunnel condition by a visual inspection, coupled with local hammering for checking the deterioration degree of the blocs. It has been observed that the blocs were covered by a 0.5-1.0 cm of dust and probably the results of old steam and coal powered trains (sclerometer test does not give any result). Then, the blocs were characterised by a 2 cm thick of highly weathered material (sclerometer testing gives results typical of weathered rocks: 9-13). Below this stratus the sound material was finally found (sclerometer test gives results typical of sound rock: 26-39). The majority of the joints in the masonry lining was highly weathered or almost completely empty mainly due to the water circulation behind the lining and
infiltration through joints. A few dripping points were observed too.
