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A five-million-pound tunnel box gets a “big push”

The King Road grade separation required creating an underpass to carry the road beneath four active rail lines and a creek while minimizing disruption to commuter trains, freight rail service, and the adjacent freight yard.

Before long we will all be able to drive underneath the rail line and never again have to wait for a train to go by on King Road.

Burlington Gazette

Awards

2014 Grand Award, American Council of Engineering Companies

2014 Hamilton Halton Project of the Year (Transportation)

2014 Award of Merit, Consulting Engineers of Ontario

2014 Gold Award, American Council of Engineering Companies (Massachusetts)

2013 OPWA Project of the Year, Ontario Public Works Association

Opportunity

Burlington, Ontario, is located in the densely populated and densely industrialized Golden Horseshoe of Greater Toronto and Hamilton. King Road is a vital link in Burlington. It is one of the few routes that extend north from the shores of Lake Ontario, across the CN rail tracks and Highway 403, to the northwest of the city.

The railway crossing on King Road is one of the busiest in the city. Almost 100 trains cross each day, causing significant delays to drivers. According to the Burlington Gazette, the recent expansion of GO Transit’s train service to Aldershot Station increased rail traffic to the point where a grade separation was needed.

The project was daunting, because it required creating an underpass to carry King Road beneath four active rail lines and a creek while minimizing disruption to commuter trains, freight rail service, and the adjacent freight yard.

Solution

Solving the problem required an international blend of geotechnical, structural, transportation, and construction management experts. This expertise was provided by HMM, a joint venture of Mott MacDonald and Hatch.

The joint venture team proposed building the reinforced concrete underpass “box” beside the rail tracks and then, while railway freight was diverted to a single track constructed adjacent to the work zone, using an open-cut bridge-jacking technique to slide it into place. To reduce disruption to commuters, jacking the box into place under the tracks, known as the Big Push, had to be completed during a three and a half day rail closure over the Thanksgiving weekend of 2012.

The completed tunnel box weighed five million pounds. “No one had ever moved an object this big, weighing this much before,” the Burlington Gazette reported. “And the time frames were wickedly tight. It had to be done over a long weekend and it had to be done on time — thousands of commuters on the Hamilton to Toronto GO train lines were depending on those trains.”

To prepare for the Big Push, contractors diverted a creek, built a supporting wall from steel tubes filled with concrete, and installed a diversion rail track that could handle freight trains while construction was going on. At the start of the Big Push, before the tunnel box could be slid into place, contractors removed a segment of the four rail lines and hauled away almost 800 truckloads of fill from under the tracks.

Despite rainfall that delayed construction by 11 hours, the King Road project was done on time and with no injuries. Using an innovative technique, hydraulic pressure was introduced underneath portions of the box, allowing the weight of the enormous tunnel box to sit primarily on the sliding mechanisms to help reduce friction as it was eased into place with hydraulic jacks. The roof of the tunnel was then backfilled, rail ballast put in place, and the track replaced and tamped down so that train service could resume safely for the Tuesday morning rush hour.

The project was documented on video, and bleachers were provided for anyone who wanted to watch in person. Bob Jurk, the city’s senior project manager, said, “I didn’t realize I’d had nothing to eat until 2:00 in the afternoon when Metric, the company doing the excavation work, told us all that there was a truck filled with pizza for everyone. That kind of thing doesn’t happen on construction sites these days.”

Time-lapse photography of this engineering feat is available in the video “72 Hours in 72 Seconds.”

Outcome

In a statement released in October 2012, City Councillor Rick Craven summed up the benefits of the King Road project:

The new underpass is critically important to the future of Burlington’s west end. It will: make it easier for traffic to get to and from the North Service Road, reducing pressure on Plains Road, improve access to downtown and Joseph Brant Hospital for Tyandaga residents, eliminate traffic congestion in the immediate neighbourhood, caused by train crossings (which on occasion has completely shut down the adjacent residential streets), and finally, it will serve as a catalyst for the long-term plan to open up the nearby “employment lands.”

The Burlington Gazette put it more concisely, writing that “before long we will all be able to drive underneath the rail line and never again have to wait for a train to go by on King Road.”

The paper predicted that when the King Road crossing had its grand opening, “every elected official still breathing will show up to have their picture taken.”

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