History has been made twice over at Turkey’s Eşme-Salihli Railway Tunnel where a 13.77 m (45.18 ft) diameter Robbins Crossover XRE TBM has set new world records for best day, week, and month in the 13 to 14 m (42.6 to 46 ft) diameter range. The machine broke all three records first in May 2021 with 25.3 m (83 ft) in one day, 117 m (383.8 ft) in one week, and 345.6 m (1,134 ft) in one month, then again in June with 28.5 m (93.5 ft), 133.2 m (437 ft), and 455.4 m (1,494 ft) respectively. The TBM, which sat in storage for seven years before being newly upgraded for this project, proves the robust durability of Robbins machines.
The Crossover TBM surpassed all previous performance rates by a machine in its size range. The closest another 13 to 14 m (42.6 to 46 ft) machine has come to these numbers was a 13.7 m (45 ft) diameter mixed ground TBM that achieved a 7 m (23 ft) average per day and a best day of 12 m (39 ft) at the Eurasia Tunnel project.
Onur Kansu, TBM Manager for project contractor Kolin Construction, attributes the machine’s success to the team operating it: “The most important reason for achieving fast advance rates is that we have an experienced and qualified team. If we open it up even further, such a team allows us to anticipate the malfunctions and to go to the solution in a very short time. In addition, all necessary maintenance is carried out on time, and the appropriate consumables are selected to increase the performance.”
The machine launched on its 3.05 km (1.90 mile) bore at the end of March 2021 as part of the Ankara-İzmir High Speed Railway Project for the Turkish State Railways (TCDD). Thus far the machine has encountered a mix of mainly mudstone with gneiss. “When we look at the overall tunnel geology.’ said Kansu, “We are excavating in complex and weak ground. In this geology, the advantages of the Robbins XRE TBM are highly favourable. The Robbins XRE TBM shows high performance in both complex and weak ground. It should also be noted that the TBM is very strong when looking at parameters such as torque and thrust.” To get through the challenging conditions, the large diameter XRE has a number of unique features. The large diameter design enables both a screw conveyor and belt conveyor to remain in place, enabling swift conversion between modes, and operation in full EPB and hard rock modes.
Regarding the future of the Turkish tunnelling industry, Kansu is optimistic about the effects these new records will have saying: “It has been seen how well the engineers and application teams in Turkey have excelled in complex geologies and the large-scale tunnelling industry. At the same time, it has shown to the whole world, especially Turkey, that with the right choices, it is possible to carry out excavations of this scale and complex geology without any problems and quickly. This project will be a pioneer in the Turkish tunnelling industry, showing that faster and more economical tunnels can be built.”
Mine Development Machine
Meanwhile, Robbins’ latest innovation is making good headway on a non-circular tunnel excavation in hard rock. The rectangular TBM, known as the MDM5000 (standing for Mine Development Machine with dimensions of 5.0 m x 4.5 m) is capable of excavating a flat tunnel invert for immediate use by rubber-tired vehicles. Employed by Mexico’s oldest silver mine, Fresnillo Plc, the MDM5000 is boring a mine access tunnel in andesite and shale with quartz intrusions that has defied earlier attempts using roadheaders. The successful operation is the result of extensive discussions between Robbins, that designed and supplied the machine, with TOPO machinery and Fresnillo Plc.
“We decided to work with Robbins for their experience. A lot of people have tried to provide these kinds of machines but nobody has done it. Robbins used its experience and skills to provide us with a rectangular profile machine.” said Fidel Morin, Projects Superintendent for Fresnillo Mine.
The technology is not only useful for the mining industry, but also for many applications in civil tunnelling. While other machines have been developed for soft ground, the MDM5000 represents the first successful foray into rectangular hard rock tunnelling. “We are very pleased to add non-circular tunnelling to our wheelhouse of solutions that continues to include TBMs, conveyors, cutters, and more. We see applications for the MDM wherever a rectangular profile is needed, such as train tunnels requiring a flat invert. In a traditional circular tunnel, the invert is filled or an invert segment is needed, but with the MDM 30% less rock is required to be removed from the profile.” said Robbins President Lok Home.
With more than 1,700 m of advance thus far at rates up to 52 m in one week and 191 m in one month, the MDM is significantly faster than drill & blast excavation. “We are making history. Fresnillo is always looking for new technology, and we believe that the usage of the MDM5000 is going to be something extremely successful, not only for our company but also for the industry.” said Morin.
The MDM5000 has undergone major component enhancements during the course of its successful bore at Fresnillo mine. It was first transported to the -695 m level of the mine and underwent final assembly and launch in a cavern, where sections of the MDM were moved by crawlers and pieces were lifted by hoist. The machine is now boring a 270-degree spiral to end above the original tunnel. It will then be backed up to the original tunnel and continue driving straight ahead.
Developed for use in rock up to 200 MPa UCS, the MDM5000 utilises disc cutter technology proven on traditional, circular TBMs. During excavation a reciprocating cutterhead and swinging cutterhead motion create a rectangular cross section tunnel.
The MDM offers a number of advantages over drill and blast. MDM tunnelling has advance rates roughly twice those of a drill and blast heading, and results in smooth tunnel walls, less overbreak, and minimised ground support. The increased advance rates are partly due to the machine’s continuous progress, unlike drill and blast operations where crews must exit the tunnel during blasting for safety. In addition, simultaneous ground support installation further increases overall advance rates compared with drill and blast operations that must install ground support sequentially.