Technical–operational comparison between trench-cutters and clam excavators for concrete diaphragm construction in underground works at shallow depths

The most common excavation methods for the construction of tunnels in urban areas are the ‘cut and cover’ method and the traditional method of excavation at the tunnel face. The first method is usually used for works at shallow depths, even though it frequently involves burdensome deviations and shifting of the existing underground plants and networks. It has been used to realise the Underground Railway Link in Turin (Italy), where excavation was made using trench-cutters and clam excavators. The results of a technical–operational comparison between the two techniques are presented in this work, from which the advantages concerning the use of trench-cutters compared to the use of clamshell bucket excavators have been determined.