40 MARCH 2022 WorldWide Drilling Resource® Rectangular TBMMakes History Adapted from Information by CONEXPO-CON/AGG A new rectangular tunnel boring machine (TBM) is gnawing through rock in Fresnillo Mine, Mexico’s oldest silver mine. The innovative TBM is capable of excavating a flat tunnel invert for immediate use by rubber-tired vehicles. The Robbins MDM5000 (which stands for Mine Development Machine) has dimensions of approximately 16 x 15 feet, and is working on a noncircular tunnel excavation in hard rock. It is boring a mine access tunnel in andesite and shale with quartz intrusions which defied earlier attempts using roadheaders. The successful operation is the result of extensive discussions between Robbins, who designed and supplied the machine, TOPO Machinery Inc., and Fresnillo. 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’re very pleased to add noncircular 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 5500 feet of advance so far, at rates up to 170 feet in one week and 625 feet in one month, the MDM is proving to be an efficient machine. “We’re 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 Fidel Morin, projects superintendent for Fresnillo Mine. Over the course of this project, the MDM5000 has undergone major component enhancements. It was first lowered 2280 feet into 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 then bored a 270-degree spiral to end above the original tunnel before backing up and continuing to drive straight ahead. Developed for use in rock, the machine uses disc cutter technology proven on traditional, circular TBMs. The MDM offered incredible advance rates resulting in smooth tunnel walls, less overbreak, and minimized ground support. Editor’s Note: In between our print issues, the WWDR Team prepares an electronic newsletter called E-News Flash by WorldWide Drilling Resource®. This newsletter is filled with articles not included in our print issue. Based on readership, this was the most popular article of the month. MIN The MDM5000 excavates with a reciprocating cutterhead and swinging motion to create a rectangular cross section tunnel. Rectangular tunnel inside Fresnillo Mine.
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