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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 sup- port in various conditions employing shotcrete 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 noz- zleman 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 same examiner/educator that conducted the edu- cational portions of the program and observed the Fig. 2 field trials. In this way, all parties involved in the placement and acceptance of shotcrete on the areas of rock wall and ceiling (refer to Fig. 2). We project were in harmony. encountered overbreaks in the excavation up to 10 ft (3 m) and overall ceiling heights that General Conditions extended beyond 50 ft (15 m). The difficult access The new shotcreting program hit four initial inherent on this project made continuous shotcrete obstacles. First, under Contract CM019, the east application impossible. We would start one sec- and west caverns, in addition to all adjoining cross tion, only to have to stop and move elsewhere, passages, Y caverns, and shafts, were to be drilled due to terrain passable only on foot or by moun- and blasted. With each blast, material was exca- tain goat. vated and moved to a crusher in the lower levels. A third obstacle, which emerged in the first It was then loaded onto an underground conveyor quarter of shotcrete applications, was the fact belt and transported north, from Midtown Man- that our crew—Sand Hogs provided by Local hattan past Northern Boulevard in Queens. This #147 and some #731 Laborers—as the shotcrete excavation activity involved a three-shift nonstop underground workforce, was not allowed to rotation. Each underground phase was scheduled service the shotcrete equipment. Due to the by set internal timetables. Because we were “the scope and logistics of the project, this task was new guys on the block,” we were given low pri- the responsibility of other union crews equipped ority and had to fight for (time) space (refer to with workers and tools and established to carry Fig. 1). out a variety of maintenance tasks in all aspects Secondly, this rock removal schedule also left of the project. Although this is efficient for most us with the task of reaching nearly inaccessible operations, electrical and mechanical services Shotcrete • Winter 2014 33


2014WinShotcreteEMag
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