11 JANUARY 2023 WorldWide Drilling Resource® “Big Tex” Makes Landmark Breakthrough Adapted from Information by Robbins A crowd gathered as a large Robbins Main Beam tunnel boring machine (TBM), dubbed “Big Tex”, recently broke through in Dallas, Texas. The machine and its continuous conveyor system for the Mill Creek Drainage Relief Tunnel successfully bored five miles in chalk and shale, advancing up to 1634 feet in one month. “I think when you step back and look at what was accomplished by this team . . . the overall length and size of this tunnel, the TBM conversion, the everyday grind to keep moving forward . . . it truly is something to be proud of, professionally and personally. No single individual could reach this milestone. It took a great team of skilled individuals. I am fortunate to be a part of it,” said Nick Jencopale, senior project manager for Joint Venture Southland/Mole. Good advance rates were not the only cause for celebration: the unique project required a planned in-tunnel diameter change of the TBM from its original 38 feet to a more compact 32.5 feet. This first-of-its-kind conversion process was undertaken 1.7 miles into the bore and was not done inside a shaft or pre-excavated portal. “The TBM conversion was a unique challenge that we were excited about, and ultimately provided a more efficient method for the desired product compared to the alternative options. Hopefully, the successful conversion proved that this option can be considered for future tunnel projects,” said Jencopale. While there were many detailed steps to the conversion process, precision design of the machine was a key aspect. “We started with a smaller machine, then we made a kit, or second skin, that was slightly larger; and then when the time came, we just took that skin off. It was essentially that simple,” explained Evan Brinkerhoff, Robbins field service manager. The conversion took about four months to complete. “The Robbins Main Beam TBM (Big Tex) performed consistently throughout the duration of the tunnel excavation. There were very minor issues and little overall downtime as a result of the TBM itself,” added Jencopale. Crews encountered some fault zones, and installed rock bolts and wire mesh in the tunnel crown as needed. Due to the relatively favorable ground conditions in much of the tunnel, including low rock strength and low abrasivity, only eight disc cutters were changed during the length of tunnel bored at the larger diameter. At the point of diameter conversion, the full dress of cutters was changed. Only 14 cutters have needed replacing since. With the TBM-driven portion of the tunnel complete, work will commence to remove the machine from the tunnel and install a final lining. The tunnel is a designated critical infrastructure project for the City of Dallas, providing 100-year flood protection for areas of East Dallas which have experienced severe flooding in the past. Construction work is expected to be complete in late 2024 to early 2025. A crowd gathered as Big Tex broke through into a shaft at the Mill Creek Drainage Relief Tunnel in Dallas, Texas. C&G
RkJQdWJsaXNoZXIy NDk4Mzk=