Lovat TBMs double the expected pace

Although not yet at sports car speeds, the two 9.4m diameter Lovat TBMs building the 6.1km rail tunnels under Bologna have reported record progress for September, advancing 510m and 540m of tunnel in 23 and 30 days respectively.

San Ruffillo Società Consortile a Responsibilit à Limitata, the jv between Nesco Entrecanales Cubiertas of Spain and Ghella of Italy, is constructing the twin tube rail tunnels 6.1km long for client Ferrovie Dello Stato, the state rail agency, on the Milan-Naples line. The US$220M project will allow high-speed trains to cross the city between San Ruffillo and Fascio Salesiani as an important part of Italy's high-speed rail network.

The geology along the alignment consists of grey-blue clays, silt with gravel, sandy silts and mixtures of silts, clays and gravel In addition, the whole route falls below the water table and EPB pressures between 1.6 and 1.7 bar have been recorded to date. A reinforced concrete segmental lining is installed behind the TBMs with an id of 8.3m and od of 9.1m. At 1.5m long, each ring consists of six segments plus a key. Mucking out is by train, fed by an axially traversing shuttle conveyor that receives spoil from the trailing conveyor.

T&TI had previously been told that average daily advance was expected to be in the region of 11m per day. Current rates peak at double this at between 22 and 18m per day. The fastest machine is Emilia, the first TBM delivered to site, which started mining on 25 June 2003. With a utilisation of 23 days in September, it advanced 510m working on three eight-hour shifts. Slower than her sister, but still well above estimates is Felsinea, which managed an impressive 359 rings in 30 days utilisation. The project is due to be completed in 2007.