The Milan to Verona section is a key section of the railway plan. And the TBM tunnel between Lonato del Garda and Desenzano del Garda, is the most complex part of the route. The owner, RFI (Italian Railways) assigned it to Consorzio CEPAV Due (formed by Saipem SpA, Impresa Pizzarotti & C and Gruppo ICM SpA).
The bored tunnel is located in Lonato, a tiny scenic town on the shores of Lake Garda. It consists of two drives of total length 9,564 m (2×4,782 m) with an axis distance of 30 m, and overburden of 5-80 m.
The expected geology is mainly silt and cobblestone. A 10.03 m diameter EPB TBM supplied by CREG will be used to excavate this tunnel. The alignment is close to the town, with glaciers and glacial lake sediments underneath. What’s worse, commonly found boulders are also among the principal considerations of the tunnel construction. In addition to that, the TBM delivery period is rather short. Taking all the above concerns into consideration, China Railway Engineering Equipment Group Co., Ltd. (CREG) submitted a customized design and proposal to the Consortium and was declared winner of the tender competition in July 2018.
To deal with the complex geology and boulders, CREG adopts the following design for the machine:
The max. 6 bar water pressure in high water pressure drives: The big machine is equipped with a series of twin-screw conveyors. Single screw mode is enabled where water and earth pressure are less than or equal to 2 bar to ensure mucking efficiency and big-pebble mucking; twin screw mode is enabled with the bottom gate of front screw conveyor closed in high water pressure formation. In this case, the secondary screw conveyor, which is a shaft type screw conveyor, is used simultaneously with the primary ribbon type screw conveyor to ensure pressure balance and safe boring in high water pressure formation.
The primary screw conveyor adopts ribbon type design for pebbles and boulders (pebbles mostly with a diameter of 400 × 400 × 400mm, some larger than 500 × 500 × 700mm, occasionally boulders with a particle size of 1-1.5m; the max. allowable particle size of tunnel belt conveyor is Φ250mm). Grid is arranged above the tunnel belt conveyor to prevent pebbles larger than 250mm from going into the muck box to guarantee stable operation of belt conveyer. Mechanized big-stone transport system combined with the gripping system of segment crane transports pebbles out of the muck box.
Another challenge for the equipment is how to ensure its stable performance along the 10km long drive. CREG selects key components of critical systems including main bearings, motors, reducers, etc. with a service time of over 10,000 hours; the company also pioneers targeted design for cutterhead, screw conveyors and gantry belt conveyors, to improve wear resistance capacity and service life, and to reduce downtime.
It is a well-known fact that the differences between the Chinese and European technical standards in defining standards for the engineering industry makes it extremely difficult for Chinese products to enter European markets.
As the first exported TBM to a EU market, CREG has overcome many challenges in the course of design and manufacturing. The FAT of the machine is carried out as scheduled, thanks to the efforts of everybody involved in the project.
On June 22, 2019, the grand FAT ceremony of the big machine was held in Zhengzhou, the capital city of central China’s Henan Province. It was attended by Franco Lombardi, President and Tomaso Tarantia, General Manager of the Consortium. They boarded the 150-meter-long, 1,800-ton equipment for a detailed inspection on each system and even the bolts. As the FAT concluded, they expressed their appreciation of the design and quality.
“The CEPAV project faces complex construction challenges, and the choice of proper equipment is critical to the success of the project, and I am pleased to choose CREG as our TBM supplier,” Frank Lombardi, president of the CEPAV DUE JV, told reporters. “We believe that their high-quality products and services will become a strong guarantee of project success. CEPAV DUE is full of confidence for facing the challenges that lie ahead, with the full support of CREG.”
Tomaso Tarantia, General Manager of the CEPAV DUE JV, named the equipment as “Martina” - the name of his youngest daughter to show his satisfaction with the equipment.
Italy, as one of the first European countries to have used TBMs for underground construction, has a rich experience in this aspect. Its choice of the Italian client proves the competence of CREG products and service.
The TBM, which will be exported to Italy to help build the high-speed railway linking Milan and Verona, marked CREG’s entry into the European market, which has effectively enhanced its brand value and international influence. The machine has been shipped to Italy and will be ready to bore in May 2020.
“This project is a difficult one and is of top priority. The eyes of the entire Italian construction industry will be on us, and we have a great responsibility, but I’m sure it will be a success,” said Tomaso Tarantia.