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Aquajet on Canadian Highway Tunnel
GTS, an major infrastructure and general contractor, has taken delivery of the latest generation HVD Evolution robot from Sweden’s Aquajet Systems AB, to use hydrodemolition techniques on its contract in Montreal’s Ville Marie Tunnel. Purpose-ordered through local distributor Pompaction, it is the first HVD Evolution hydrodemolition machine in Quebec and the Maritime Provinces. The use of hydrodemolition techniques on the project will ensure no rebar damage, minimized risk of good concrete removal, elimination of dust and crystalline silica and provide a superior bond surface. It is also a substantially faster technique than mechanical removal methods and is also considerably less labor intensive. Opened in the mid 1970’s, the 3 km long tunnel is par of Highway 720, a key arterial east-west highway across the city. With more than 100 000 vehicle movements a day, it is essential that traffic restrictions are minimized.
Concrete is being removed to a depth of 125 mm exposing the old rebar. An additional 100 mm and new rebar for further strength, making 225 mm thickness, is being added. In replacing the old concrete, the opportunity is also being taken to reroute electrical and telecoms cables and fiber optics into a common conduit and install new improved lighting in the tunnel. Chequered pattern of concrete removal was specified taking into account structural design loadings of the tunnel wall. Alternate sections measuring 2,4 m x 5 m height along the bottom level and 0 – 15 m along the upper level at the portal, are undertaken at a time. Close to the portal exit two areas over a length of 15 m were found to be particularly unsound and in very poor condition. The client therefore specified that for safety of the workforce, the entire section should be removed in a single operation. GTS had initially allocated two shifts a day for the hydrodemolition process but such is the speed and efficiency of the Aqua Cutter Evolution that the contractor is working just a single daily shift for the operation.
“We had been very impressed with the performance and quality of work recognizing the potential for this tunnel project,” he said, adding, “On winning this contract we took delivery of the new unit together with the Power Pack – a PP700 and we have not been disappointed.” GTS started work on the contract in mid-August with an October 2010 completion date. Operating in “live” traffic conditions with very heavy traffic flows and working at heights of up to 15 m, it was essential that the contractor protected both its workforce and passing traffic from falling debris. As a result the robot is installed behind a protected frame and positioned on a telescopic handler for ease of access for the extended height operations. The Aqua Cutter is thought to be the only robot in the world that is able to operate at these heights of up to 15 m and this was a key factor in GTS purchasing the Aquajet system. Operating at 1000 bar the Aquajet system is using a water flow rate of 260 l/min and is achieving a removal rate in the deteriorated concrete of up to 1,5 m3/h. “Without the Aqua Cutter GTS would have used conventional jackhammers to remove the concrete,” confirmed Michel Francoeur. Using the Aqua Cutter removes damaged concrete at the speed of several hydraulic jackhammers and more than 25 times faster than hand held hammers. It also requires just 1 or 2 operatives compared with one per hammer. Hydrodemolition also eliminates the risk of “Vibration White Finger” (also known as hand-arm vibration syndrome and dead finger) triggered by continuous use of vibrating hand-held machinery.
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The GTS contract involves replacing approximately 1 km of concrete on both sides of the eastern portals directly below the Palais des congrès de Montréal (convention center).
Project manager, Michel Francoeur had previous experience with hydrodemolition techniques using a standard Aqua Cutter robot rented from Toronto for a bridge deck slab project in Montreal.
