Challenges and Solutions related to the Interaction of Soil Conditioning and Main Drive on Large Diameter EPB TBM’s - A Case History

"GENERAL PROJECT DATA The Sparvo Tunnel belongs to “Variante di Valico” project, a new 65 km highway link between Bologna and Florence, designed to renew the existing A1 route and to connect in a faster way Bologna and Flor-ence. It is composed of a 2,5 km twin tunnel excavated in a complex geological context, characterized by the presence of a series of surface landslides and methane gas. The gradient is 2.6 % and the minimum radius is 1’400 m. The internal diameter of the precast seg-ment lining, equivalent to the final section of the tunnel, is 13.6 m. MAIN TBM SPECIFICATIONS TBM Earth Pressure Balanced S-574 “Martina”, manufactured by Herrenknecht, has a theoretical excava-tion diameter of 15’615 mm. It is equipped with a conical shield 12.2 m long and four back-up gantries. The total length of the machine is approximately 130 m, weighing approximately 4’500 tons. The total installed power is 16’800 kW. The main drive has a diameter of 8’700 mm and has a triple axis roller type bearing equipped with a labyrinth system including 4 sealing lips. TIME SCHEDULE OF INITIAL TBM DRIVE A time schedule of the initial TBM drive is presented in the following list: •,August 25, 2011: start of the excavation of the 1st drive of the Sparvo tunnel •,October 29,2011: stop of the advance of the TBM for gear oil contamination and clogging •,October 29 to December 20, 2011: repair works on the main drive system and modifications on the conditioning system •,December 20,2011 to July 25, 2012: restart excavation of the 1st drive (north tunnel) and its breakthrough •,July 25 to November 29, 2012: 180° turning of the TBM, detailed check of the main drive seal-ing system and fixing problems on gear boxes, race ring, clamping ring and cutting wheel •,November 29,2012 to July 24, 2013: excavation of the 2nd drive (south tunnel) and its break-through •,August 2013 to July 31, 2014: disassembly of the TBM (first 4 months) and standstill of the jobsite for structural issues on precast concrete lining of the tunnel •,July 31, 2014 to March 10, 2015: inspection, dismantling and packaging of each part of the main drive (flange ring, gear box housing and main bearing). The various phases are described hereafter in detail."