THE INTERACTION OF THE CLOACA MAXIMA WITH THE TUNNELS OF THE C LINE
The T3 section of the construction of Rome’s metropolitan Line C will pass under the historical centre interacting with its artistic and monumental heritage. Towards the end of the section, the tunnels will run along the Via dei Fori Imperiali adjacent to the Colosseo and the Basilica di Massenzio and will pass under the two branches of the Cloaca Maxima in correspondence with the Via dei Fori Imperiali.
Since 2008 Metro C, the General Contractor for the construction of the Line C, has designed and implemented a series of non-destructive investigations in order to verify the state of consistency and conservation of the monument and to effectuate the interaction analysis in the building of the line.
The vigorous surveys carried out made it possible to clearly define the internal geometry of the Cloaca Maxima sewer system, and to determine with certainty the materials and types of masonry used as well as to ascertain the relative mechanical perimeters.
The use of laser scanner technology has provided a valid aid to the design activity as it has allowed the development of an extremely detailed survey of the internal geometry of the sewage system, as well as of the components which constitute the walls of its intrados.
The interaction analyses are of considerable importance in the design of an urban metropolitan line, in particular in the historic centre of Rome, and represent the starting point for the design of any protection works and/or systems to reduce subsidence, as well as adequate monitoring systems.
The survey will be completed during the summer of 2018, about a year before the excavation of the line tunnels, and will include defunctionalizing a section of about 150 metres of the sewerage to extend the study of the state of conservation as far as the ancient structures below the “sliding floor” of the water in the system and, if necessary, intervene with certain specific consolidations.
The defunctionalization will be carried out with the installation of two vertical metal sluice gates with a lateral self-sealing clamping system and with three metallic pipelines 5mm in diameter for flow continuity. The proposed idea is that it will also be equipped with an alarm system in case of a sudden rising of the water levels. The control of the flow coming from the Via Cavour pipeline involves the construction of a single small barrier equipped with an adequate controlling of small overloads of water, but of a rapid release in case of macro-atmospheric events in accordance with the security system of the gates for operator safety. Thus sized the system is able to dispose a nominal flow rate of 5.000 m3/h against a normalized flow of 1600 m3/h at a surface height of 35cm.
Finally, during the excavation of the tunnels, a large and complex project of monitoring the monument will be put in place inside the ancient sewer system in order to keep the data monitored in constant correlation with the results of the studies carried out in the planning phase.
Engineer Eliano Romani Metro C Design Manager