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Synchronized SBUs Bore Below Mississippi River: Multi-Tasking Auger Bores Move Muck For Force Main
“These are the longest crossings I have done with the SBU-A. There tends to be a little torque buildup on the augers at long lengths, so you need to have very good augers when you are doing it. Other than that, the SBUs work great for rock. When we used the old style heads with bullet teeth, every 40 feet you had to pull the head out, change the teeth, and still the wing cutters would wear down even more. That’s the nice thing about the SBU -- you put it in the ground, it starts boring, and it keeps going,” said Dixon.
Both SBU-A bores were completed within the project schedule and within line and grade specifications. The 60-inch bore wrapped up on Dec. 20, 2011, while the 42-inch bore broke through on Feb. 10, 2012.
Overall, L.J. Keefe and the companies involved were pleased with the crossing construction, citing both quality equipment and an experienced work crew. “It’s dedicated employees like my superintendent Frank Keane, with 30 years of experience, that ensured a successful outcome for this project. We didn’t find any production drop off as the bores progressed,” said Keefe.
The contractor also made use of technical assistance provided during SBU-M startup and throughout the bore. Field Service Consultant for Robbins, Scott Fisher, came to the site to advise on aspects of machine operation.
Keefe says the company has more plans to use SBUs on projects in the area and throughout the Midwest: “The biggest benefit is in being able to mold our current technologies with SBUs, using them in conjunction with ABMs, or in conjunction with our existing tunneling equipment. We can use our existing equipment with the specialized Robbins equipment to lower costs and shorten project schedules.”
How Small Boring Units Work