Speedy Tunnelling with Lovat TBMs on High Speed Rail Tunnels in BolognaThe San Ruffillo JV between Necso of Spain (now Acciona Infraestructuras) and Ghella of Italy has reported record progress by their pair of Lovat EPB TBMs in Bologna. Salini is also part of the JV, although the building work is managed by Necso and Ghella. The JV is building a 6.1 km twin-tube railway tunnel under the city of Bologna, Italy for owner Ferrovie dello Stato. Italferr is in charge of the work supervision. These cross-city high speed tunnels are the continuation of those already completed on the high speed link between Bologna and Florence (click here and here). Visit www.acciona-infraestructuras.es and www.ghella.com/utilities/SanRuffillo.pdfOther underground structures include 5 m-long 10 sq m crosscuts built by traditional method every 500 m (250 m while the TBMs progress). These cross passages have to be mined in a very tight schedule from the tunnel where a 4-day break is being observed, while tunnelling stops in the parallel tunnel just to do the reinforcement works in these cross passages.The cutting head drive for each TBM has 2,700 kW installed power with a speed from 1 rpm to 2.1 rpm and a maximum torque of 25,000 kNm. Equipped with 36 propulsion cylinders the propulsion capacity of each TBM is 10,000 tonnes. Visit www.lovat.comProgress has been remarkable, with a peak of 24 1.5 m-wide rings installed in a single day, under working pressures comprised between 1.5 and 2 bar. The entire tunnel alignment is below the water table. EPB pressures were measured from 1.6 to 1.7 bar. In September 2005 alone, the sister machines have drilled 1,050 m of tunnel. The first Lovat TBM delivered to site, christened Emilia, completed 340 rings in 23 days (in three eight-hour shifts) for 510 m of tunnel. Also for September, its twin Felsinea completed 359 rings in 30 days. There was no stoppage for this machine. For the entire month, Felsinea completed 540 m of tunnel. Progress as of 15th December, 2005 was 4,200 m for TBM 1 and 4,100 m for TBM 2. Each tunnel is scheduled to breakthrough in January 2007. The geology is alluvial soils consisting of gravels, sands, silts and clays. The spoil is removed using two 40-tonne locos pulling seven muck wagons. Two muck trains are alternately used. The TBMs utilise a unique muck removal system. The shuttle conveyor was designed to fill stationary muck cars in either of the two trains. To accomplish this, the conveyor moves axially along the gantry as it receives excavated material from the trailing conveyor. The shuttle conveyor discharges the muck at either end (reversible belt direction) to fill first the rear set of the muck cars and then the front set. A hydraulically controlled chute deflects the discharging material to the left or right side of the tunnel.The tunnel lining is made of prefabricated rings of reinforced-concrete segments with an inner diameter of 8.3 m and an outer diameter of 9.1 m. Each 1.5 m-long ring is comprised of six segments and a key. The carrousel facility of moulds which produces the prefabricated segments has been supplied by CBE and the production of the segments has been subcontracted. Click here. Visit www.cbe-tunnels.com and www.tav.it 02/06.