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Goin’ Underground following the applicable training curriculum and examining procedure of ACI Committee C660 be established for the purpose of qualifying craftsmen for application of shotcrete specific to the require- ments of each underground project. This was not and could not be an ACI-sponsored program, but it was deemed acceptable by the project engineer after a comprehensive review. The program was developed and presented by qualified, creden- tialed ACI C660 examiners and educators. This new training and qualification program required background information describing previous shotcrete experience, which was sub- mitted either by the individual or the union for each candidate. The shotcrete “résumé” was reviewed by the project engineer, the examiner/ educator, and others as required. This program incorporated classroom instruc- tion of 4 to 6 hours, including topics such as basic concrete technology and practice, shotcrete Fig. 1 application, equipment operation and mainte- nance (directly related to shotcrete), ground support in various conditions employing shot- crete in combination with rock bolts, lattice girders and other support components, quality control, safety specific to shotcreting, and project requirements. It also included field trials such as practice shooting, the shooting of test panels to demonstrate application skills, and lab testing to confirm quality of materials placed. Finally, the program required field supervision by a qualified examiner/educator during initial shotcreting by the nozzleman on the project. One of the priorities of this program was to ensure the continued presence of quality assur- ance and inspection personnel employed by the owner and designer, as well as quality control efforts by the contractor. The ongoing quality assurance and inspection were provided by the Fig. 2 same examiner/educator that conducted the edu- cational portions of the program and observed excavation activity involved a three-shift nonstop the field trials. In this way, all parties involved in rotation. Each underground phase was scheduled the placement and acceptance of shotcrete on the by set internal timetables. Because we were “the project were in harmony. new guys on the block,” we were given low priority and had to fight for (time) space (refer to Fig. 1). General Conditions Secondly, this rock removal schedule also left The new shotcreting program hit four initial us with the task of reaching nearly inaccessible obstacles. First, under Contract CM019, the east areas of rock wall and ceiling (refer to Fig. 2). We and west caverns, in addition to all adjoining cross encountered overbreaks in the excavation up to passages, Y caverns, and shafts, were to be drilled 10 ft (3 m) and overall ceiling heights that extended and blasted. With each blast, material was exca- beyond 50 ft (15 m). The difficult access inherent vated and moved to a crusher in the lower levels. on this project made continuous shotcrete appli- It was then loaded onto an underground conveyor cation impossible. We would start one section, belt and transported north, from Midtown Man- only to have to stop and move elsewhere, due to hattan past Northern Boulevard in Queens. This terrain passable only on foot or by mountain goat. Shotcrete • Summer 2013 39


2013SumShotcreteEMag
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