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Design of Flexible Formwork & Temporary Support System
The track is 1700m (5577.5’) long with an elevation difference of 150m (492’), with an iced surface area of approx. 6800 square meters (73, 195 square feet). The entire superstructure of the track was constructed of reinforced shotcrete with embedded refrigeration pipes. The track has an average cross sectional thickness of 150mm (6”).
The objective was to design the track formwork and a steel base frame to support the weight of the shotcrete, rebar, refrigeration pipes and the live load of the placing crew – all with negligible deflection. schedule.
The steel base frame was covered with a formply decking system to form the soffit and haunches of the track. This system had to be designed with such flexibility, to be able to be used at any location on the whole track, including the section with over 3.6m high wall and section with only 1.2m walls. Once the formply was in place the refrigeration pipe support jigs were installed next. These support jigs were custom fabricated to a 1 mm tolerance to control the track profile every 1.5m on station. I developed a bending table with removable steel pins for the bending of the jigs.
Completion and testing of the refrigeration system was followed by installation of the top mat of reinforcing. Stayform mesh was installed along the backside of the track and formwork for the upper and lower lip of the track installed. Shotcrete was applied to the inside surface of the track encompassing the top and bottom layers of rebar and the refrigeration pipes. The shotcrete was applied in various layers due to the complex geometry and the density of the rebar mats and refrigeration pipes. The outermost layer of shotcrete was then applied to the inside face, this was to become the riding surface of the finished track. As such, this surface was required to be finished to a tolerance of less than 3mm in 3 m. The entire section ranging in length from 40m to 70m remained under the tent structure and was constantly misted to ensure proper curing of the section.
The track at the Whistler-Sliding Centre is one of the most technically challenging applications of shotcrete to date. The density of the rebar coupled with the tight spacing of the refrigeration pipes and 150mm cross sectional thickness all combined to make the proper placing of shotcrete a major challenge. We were able to achieve a near perfect cross section. The high finish tolerances of this project also added to the complexity of this project. Support jigs were fabricated and installed to millimeter tolerances. Multiple quality control checks were implemented and profiles checked and rechecked with a laser to ensure compliance with the specifications. The combination of attention to detail at the design level, the construction level and the shotcrete placing level all result in a truly world class facility. This project was an excellent example of the versatility and adaptability of shotcrete.