THE new horse tunnel from the stables through to the mounting yard at Melbourne’s Flemington Racecourse remained ‘on track’ for a totally waterproofed finish, thanks to a range of state-of-the-art waterproofing solutions from BASF Construction Chemicals . Part of a $13 million redevelopment of Flemington’s famous Birdcage area, the new tunnel has been designed to improve safety at the track by diverting horses away from crowds as they make their way from the stalls to the mounting yard before each race.
As is often the case with tunnelling and underground construction projects, the Flemington Horse Tunnel presented a number of significant design, engineering and construction challenges. Together with the tight construction time-frame (the redevelopment had to be completed in time for the Makybe Stakes in early September 2007), the combination of location, geology and hydrology presented a major waterproofing challenge for the Victoria Racing Club (VRC). Gemma Nolan, business development manager with Austress Freyssinet, explains: “The Flemington Racecourse is located immediately adjacent to the Maribyrnong River. This combined with the fact that the tunnel is being constructed below the water table in Coode Island Silt, means that the performance of the waterproofing methods and materials used are critical factors in the success of the project.”
“The VRC wanted to be sure that the finished tunnel was totally waterproofed and didn’t leak, and what’s more, that it would remain that way for the long-term. With that in mind, we worked with the VRC, architects the Buchan Group, engineers Grogan Richards, and the builder Construction Engineering, to develop a design concept and specification for the tunnel waterproofing,” she said. Measuring some 193m from ramp to ramp, the project incorporates 80m of cut and cover tunnel with internal dimensions of 3.5m x 3.6m. Following the excavation works and the establishment of a blinding slab, Bentonite matting was laid down prior to the tunnel’s floor slab being poured. This was then followed by the construction of the poured-insitu walls and roof sections. For maximum waterproofing effectiveness, all joints – both along and between the floor, wall and roof sections – were fitted with the Masterflex 900 Fuko Injection System reinjectable hose system.
Specifically designed for jointed concrete structures which are subjected to hydrostatic pressure on one or both faces of the structure, Masterflex 900 hose is installed along the joints and then injected with an appropriate injection material – causing it to swell and seal any voids along the joint. Importantly, Masterflex 900 is able to be injected at any time, thereby allowing it to cater for slight movement and/or expansion of joints which can occur over time. For the Flemington Horse Tunnel project, the Masterflex 900 hose has been installed as a secondary waterproofing solution, which can be injected with Masterflex 801 – a highly flexible methacrylate crack injection resin if need be.
The second stage of the tunnel waterproofing process incorporated an application of Coniroof 2113 to the external surfaces of the tunnel roof and walls. A member of the Conipur family of waterproofing membrane systems, Coniroof 2113 is a waterproof membrane system comprising a primer coat followed by a layer of Conipur M810, a highly elastic polyurethane resin-based crack-bridging membrane. Suitable for use on vertical and horizontal concrete substrates (including inverted roofs), the Coniroof 2113 system delivers the ideal combination of outstanding long term durability, high elasticity and extremely fast curing time.
Source: Construction Contractor