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Goin’ Underground A third obstacle, which emerged in the first operations, electrical and mechanical services quarter of shotcrete applications, was the fact were often not available when required on our that our crew—Sand Hogs provided by Local project, which resulted in downtime and quick #147 and some #731 Laborers—as the shotcrete changes in procedure. Available maintenance underground workforce, was not allowed to crews had a variety of workers with vastly dif- service the shotcrete equipment. Due to the ferent talents. While the range of expertise was scope and logistics of the project, this task was ultimately an asset to the project, in the short- the responsibility of other union crews equipped term, it inhibited a uniform and productive with workers and tools and established to carry shotcrete application. For example, if a large out a variety of maintenance tasks in all aspects robotic machine went down and was in dire need of the project. Although this is efficient for most of service, its maintenance received no priority but was added to the list on a “first-come, first- served” basis. The final obstacle was that the areas to be shot - creted were also high-traffic sites, accessed by workers in many trades. It was a bottleneck for all those involved and made implementation of the shotcrete process and schedule very challenging. Shotcrete As the accepted training and qualification program was put into place, we began our journey along the learning curve. The crews and manage- ment settled on hand-nozzling with the aid of man lifts. This was an important stance to take in deference to the qualifications of the workers. We strongly believe that no matter how many class- room sessions we had (2 full days for each noz- zleman, on average) or how many hours were spent perfecting technique on the robotic machines, the best way to learn quality shotcrete Fig. 3 placement was to actually grab the nozzle and shoot by hand. Under the observation of a qualified supervisor or previously qualified job foreman, we could start with the nozzle in a low-risk wall or bench shooting to acquire hours of practice. Full quali- fication came after an accepted number of hand- nozzling hours were documented by the approved qualification trainer. It was of great benefit for the nozzleman to have a qualified trainer by his side, giving tips while shooting or discussing key issues with the foreman so he, in turn, could relay advice to the general crew. It should be pointed out that our qualification was geared toward the entire crew and full shotcrete process, not just the workers holding the nozzle. Both dry- and wet-mix shotcrete materials and equipment were used. With a 6 in. (150 mm) slick line, wet-mix concrete was sent from the street through a re-mixer down to the tunnels and into the Putzmeister Shotcrete Technologies’ shotcrete pumps. Despite both the harsh physical environ- ment and the carelessness demonstrated by some Fig. 4 tradesmen in moving equipment from one 40 Shotcrete • Summer 2013


2013SumShotcreteEMag
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