THE TUNNELS OF COCCEIUS IN NAPOLI: AN EXAMPLE OF ROMAN ENGINEERING OF THE EARLY IMPERIAL AGE

摘要

The Greek Campanian L. Cocceius Aucto, active in the early imperial age. is believed to be the architect of the temple of Augustus in Puteolis and of the three largest known Roman road tunnels, all in the Phlegrean region east of Naples. They are: (?) the Crypta Neapolitana, connecting Naples to Puteolis as an alternative to the longer way through the hills; (ⅱ)the Grotta di Cocceio, connecting the Lake of Averno to the citadel of Cumae, and (ⅲ)the Grotta di Seiano, crossing the hill of Posillipo to access the villa of Vedius Pollio. These three tunnels are excavated in the pyroclastic materials of the Naples area (tuff, pozzolana) and range in length between 700 and 1000 m, more than twice the next longest known Roman road tunnel. Two of them have been restored in the XIX century, and can still be travelled; the Crypta has been in regular use from the time of construction until 1885, but at present is partly collapsed. The principal features of these three engineering masterpieces are reported and compared. The Crypta Neapolitana and the Grotta di Cocceio are examined in some detail, analysing the stress state and comparing it with the mechanical properties of the rock and with the occurrence and type of damages.