The largest TBM ever used in Europe has successfully completed its drive in Italy. The supersized 15.87m diameter Herrenknecht EBPM excavated the 7.5km Santa Lucia highway route through the Apennines. Working with contractor Pavimental the new TBM was designed in particular to protect the site crew from the expected methane gas deposits in the ground. A comprehensive alarm and protection system warned against the dangers of encountering methane gas during the advance.

The large three-lane Santa Lucia tunnel is a key project in the expansion of the Autostrada A1 between Bologna and Florence. The new underground highway will minimise the likelihood of accidents, improve travel times and reduce consumption of gasoline and diesel by the tens of thousands of cars and trucks that use the highway each day.

Following 12 months of design and manufacture, the assembled TBM was ready at Herrenknecht in Schwanau in August 2016 for formal acceptance by the contractor and representatives of the client, the Autostrade per l’Italia. After the start of tunnelling in July 2017, the Pavimental crews operated the mega machine at progress rates of up to 122m per week and excavated a total of about 1.5 million m³ of rock and soil.

The Santa Lucia machine at 15.87m diameter is larger than the previous European record holding TBM also used in Italy, also on the Autostrada A1 between Bologna and Florence, and also manufactured by Herrenknecht. The 15.55m diameter EPBM was used by Toto Costruzioni Generali and its JV partners, Vianini Lavori and Profacta, to excavate the twin 2.5km long tubes of the Sparvo highway tunnel between 2011 and 2013 and completing the second drive in eight months and less than two years after starting the first tube in August 2011.

Manufacture of the largest EPB TBM for a European project, the third largest the world has ever seen, and the second largest ever manufactured by Herrenknecht of Germany, is complete.

Gigantic proportions of the 15.87m Santa Lucia TBM

Representatives of the client, the Italian Highways Authority Austostrade per l’Italia S.p.A, and its appointed contractor Pavimental S.p.A. gathered at the Herrenknecht factory in Schwanau to complete a comprehensive technical inspection and to then formally accept the 4,800-tonne mega-machine. The official ceremony took place last Monday (29 August).

At 15.87m in diameter the titanic machine is 25cm larger than the previous European record-holding shield – the 15.62m EPB, also manufactured by Herrenknecht, for excavation of the 2.5km twin tunnels at Sparvo as part of a phased renewal and upgrade of the A1 highway between Bologna and Naples.

The latest mega-machine to come out of the Herrenknecht factory is the largest the company has ever manufactured in its European facilities, and will be used to excavate the 7,528m Santa Lucia Tunnel in the Apennine mountain range, located between Barbarino and Firenze Nord (Fig 1). A 59km stretch of the A1 between Barbarino di Mugello in the north, and Firenze Incisa Valdarno in the south, is being widened in four lots (one of which is completed) through the construction of up to three new lanes for southbound traffic, with the existing four-lane highway, two in each direction, being turned into the northbound route.

The machine, which will drive through a heterogenous geology, features a drive power of 8,750kN, and a torque of 101,296kNm. The contractor for the job, Pavimental, is 20% owned by the client company, and 0.6% owned by Italian company Astaldi.

Gennario Tozzi (Pavimental Head of Group Infrastructure Development, left), and Franco Tolenntino (Pavimental Chairman, centre), accepting the mega-TBM from Martin Herrenknecht

Fig 1. A1 highway near Firenze

In the coming months, 13 Herrenknecht TBMs will be operational in Italy – eight of them measuring more than 8m in diameter. On the A1 route alone a total of 44 new road tunnels are planned – including the Santa Lucia Tunnel. The route will be opened to traffic in 2019.

Only two machines in the world have been manufactured to a larger diameter than the enormous 15.87m EPB that will excavate the Santa Lucia Tunnel– the 17.48m Hitachi-Zosen EPBM that is currently excavating the Alaskan Way Viaduct Replacement Tunnel in Seattle, USA; and the world-record 17.6m Herrenknecht machine that was built in the company’s Chinese factory for the currently under construction Tuen Mun–Chek Lap Kok subsea highway link in Hong Kong.