Abstract
Problem statement: The high-velocity railway link between Bologna and Firenze (Italy) is today under construction and several tunnels have to be excavated for this purpose, some of these using TBMs. A small diameter tunnel, named Cunicolo ginori, was realized by TBM parallel to a large railway tunnel (Vaglia), at the distance of only 35 m. Approach: The Vaglia tunnel had been excavated by conventional methods and provided, thanks to a detailed survey and a systematic geotechnical monitoring (rock quality evaluation and convergence measurements) the characterization data of the crossed rock mass; moreover the TBM performance data in Cunicolo ginori were continuously monitored. A tunnel stretch, 587 m long, was recorded and the analysis of the data from both surveys allowed to correlate the geomechanical parameters of the rock-mass to the TBM performances (net advancement rate, thrust, specific energy). Results: Based on this large amount of data a new system to predict the net TBM advancement rate for a tunnel in rock masses of known geological and geomechanical characteristics was then developed. Also the Utilization Coefficient (CU) can be correlated to the rock quality Indices: The net advance rate and the utilization coefficient provide a mean to foresee the gross advancement rate and to evaluate the suitability of a machine for the excavation of a tunnel. Conclusion: In this study, an analysis had been carried out on about 587 m of a service tunnel, excavated by a TBM in a flysch formation.
Highlights
Amongst the main railways connections along the Italian Peninsula, the Bologna-Firenze link belongs to the Milano-Napoli connection and has a long history: From the first attempts of planning a railway in the 19th Century to the present railway connection, to the railway under construction for the high speed trains (TAV).The new link Bologna-Firenze, planned in 1992, is 78 km long, 73 of whose are placed in tunnels, with a slope of 1.2% and an altitude of 414 m above sea level.One of the longest tunnels of this connection is Vaglia tunnel, around 18.5 km long
Deduction of possible relationships between the Penetration per revolution: Penetration per revolution rock mass characteristics and the Tunnel Boring Machine (TBM) performance is one of the most important parameters often used to parameters
The explication revolution was deducted), excavation specific Energy should be due to the fact that the TBM operator has (Es) and utilization coefficient
Summary
Amongst the main railways connections along the Italian Peninsula, the Bologna-Firenze link belongs to the Milano-Napoli connection and has a long history: From the first attempts of planning a railway in the 19th Century to the present railway connection (the so called Direttissima), to the railway under construction for the high speed trains (TAV).The new link Bologna-Firenze, planned in 1992, is 78 km long, 73 of whose are placed in tunnels, with a slope of 1.2% and an altitude of 414 m above sea level.One of the longest tunnels of this connection is Vaglia tunnel, around 18.5 km long. Amongst the main railways connections along the Italian Peninsula, the Bologna-Firenze link belongs to the Milano-Napoli connection and has a long history: From the first attempts of planning a railway in the 19th Century to the present railway connection (the so called Direttissima), to the railway under construction for the high speed trains (TAV). The new link Bologna-Firenze, planned in 1992, is 78 km long, 73 of whose are placed in tunnels, with a slope of 1.2% and an altitude of 414 m above sea level. A service tunnel (called Cunicolo ginori) has been driven, parallel to Vaglia, at the place of Adits for the passengers evacuation. The service tunnel was linked with the main tunnel by means of 20 by-pass, spaced 250 m. The characteristics of the railway line ( curvature radius 5450 m, platform width 13.6 m, distance between rails 5 m, maximum grade 1.2%), involved to adopt for the Vaglia tunnel a cross section of 82 m2
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