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Goin’ Underground robotic equipment being used for rock support and a tunnel lining. Improved technology with new systems includes use of accelerator injection systems (Fig. 5) that automatically adjust the amount of product to match the stroke of the concrete pump. I have been involved with the ACI Nozzleman Certification program for over 15 years, being one of the founders of the program and one of the first ACI Shotcrete Nozzleman Certification examiners. With my detailed knowledge of the ACI certification process, I have explained to many tunneling contractors and engineers why they need ACI Nozzleman Certification for the underground shotcrete applications, both handnozzled and robotically placed. Though the term “robotic” is widely used, it often introduces some misconceptions on what the equipment can actually do. In manufacturing plants, robots are usually programmed to endlessly repeat a defined set of operations. It may be welding an auto body or assembling a complicated piece of electronic equipment. In these manufacturing cases, the environment, material supply, and final assembly are well-defined. However, in shotcreted work, we don’t have the “well-defined” final assembly—we have a host of variables: • The underground receiving surfaces are normally quite variable; • There is a varying amount of reinforcing; • There may be varying thicknesses due to overcut of the rock; • Concrete consistency may vary based on age of the mixture; • Air and water volume and pressure may vary with the length of delivery hose; and • Temperatures may vary and affect the thickness layers may achieve. Really, in underground shotcrete, the robotic equipment is a tool for holding the nozzle, and the nozzleman remotely manipulates the nozzle position. This is similar in some ways to the concrete pump operator on a large boom truck who controls the pumping and placement at the end of the delivery hose, or maybe equivalent to a drone operator who controls the location and speed of the flying drone. Though we use the term “robotic,” shotcrete placement is not preprogrammed or automated in a closely controlled environment. The quality of the final concrete in an underground application depends on the skill of the nozzleman and their knowledge of the various factors essential to quality concrete construction. Thus, the Fig. 5 Fig. 6 nozzleman must be fully educated on the importance of material selection, properly sized and maintained equipment, proper placement techniques, testing requirements, safety, and finishing (Fig. 6). A quality underground nozzleman should have the basic knowledge and skill for hand-nozzling first, and then they can add the skill to remotely manipulate the nozzle with the robotic equipment. ACI Shotcrete Nozzleman Certification helps to confirm in a standardized and rigorous way the nozzleman’s knowledge of all aspects of basic shotcrete placement, and their ability to properly shoot the performance panel. The ACI Nozzleman Certification program covers the fundamentals for the shotcrete process Shotcrete • Fall 2016 41


2016FallShotcreteEMag
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