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Constance Walter

Moving equipment directly to the Yates Shaft just got a whole lot easier. For several years, equipment from the 4850 or other levels that needed repair was brought to the headframe then loaded onto forklifts and driven down to the shop yards. But over the past couple of years, Sanford Lab has been working to rehabilitate 192 feet of the Yates Tunnel, which stretches more than 200 feet. The project was completed Sept. 7, 2016.

?The tunnel can now be used for its original purpose,? said Andrew Brosnahan, facilities engineer. Brosnahan and Mike Johnson, engineering project manager, oversaw the rehabilitation of the project. ?Before this project was completed, no one could use the tunnel. Now, we can get work done more efficiently and safely.?

Traditional ground support techniques, which involve the use of rock bolts and mesh, were not an option on this project, because of the low overburden above the tunnel and the broken ground, said Bryce Pietzyk. ?We knew we had to develop an innovative, long-term structure. We worked with several entities to find it.?   

The solution came in the form of a steel archway system that was developed in partnership with True North Steel, Donovan Construction, W-D Masonry, the South Dakota School of Mines and Technology Mining Department, RESPEC and Sanford Lab. The solution? Prefabricated steel archway sections.

Working from the outside toward the ramp, crews from Donovan Construction removed old timber sets and other debris?8 feet at a time. As each section was cleared, they installed 8-foot long, 4-foot tall corrugated steel bases on either side of the tunnel, then placed two 4-foot sections of angle-iron steel archways that span the tunnel on top of the base. 

Next, a team from W-D Masonry backfilled the void above the section with concrete, pumping it upward through taps in the rib of the tunnel. Above one section, the void was so high?more than 20 feet?crews had to put a tap through the Yates Crusher room floor and pump the concrete down to ensure the space was filled. 

?I?m really pleased with the work the contractors did. And our staff did a great job securing each area so the work of removing timber and installing the new tunnel could be done safely,? said Tim Baumgartner, facilities infrastructure director. 

In the end, 47 steel archways and 24 steel bases were installed, with nearly 700 cubic yards of concrete poured. The tunnel is 10 feet tall and 10 feet wide. 

?This tunnel is really solid now and will last a long time,? Brosnahan said. ?More importantly, it provides safer access from the shop yards to the ramp.?