INNOVATION January-February 2016

like explosives to bring down avalanches in a controlled way. We use explosives on three highways in BC now; new technology means we can trigger them remotely. Finally, you go to permanent mitigation— permanent engineered structures—like snow sheds and steel-wire snow nets or fences, which can hold an entire winter’s worth of snow.” The BC Ministry of Transportation and Infrastructure’s litmus test for mitigation, says Jones, is based on whether experts believe an avalanche big enough to bury a vehicle will occur at a hazardous location along a highway more often than once every 30 years. If it meets that test, the department will look first at temporary road closures, then at explosive controls, and then at protection structures. The Coquihalla Highway is a prime example of good design combined with the right mitigation measures. Peter Schaerer, P.Eng., was responsible for identifying avalanche hazards along the route and recommending potential solutions, including an above-surface snow shed and earth-filled deflection berms. As a result, except for a massive avalanche in 2007 that closed the road for eight days, the highway has rarely been closed due to avalanches or rockfalls for more than a day since it opened in 1986. In addition, BC currently boasts the only two snow-avalanche fences in Canada, located along the transportation corridors between Terrace and Prince Rupert, and between Golden and Revelstoke. Jones was part of the project team for the installation on Highway 16, west of Terrace. “The snow nets are 82 metres of three-metre-high steel mesh,” he says, “installed in three rows in the avalanche zone,” an area that causes about 80 percent of all closures on the highway. It took a seven-person crew, flown in daily by helicopter and secured by ropes along the 40- to 55-degree slope, 325 metres above the highway, six weeks to complete the installation. E xploders cost about $100,000 to $250,000 each, nets and fences cost hundreds of thousands of dollars, and rockfall and snow sheds cost in the millions. With that kind of money at stake, you want to be sure your permanent rockfall or avalanche structures are the best they can possibly be. Duncan Wyllie has a patent pending on a rockfall structure that builds on research and development already done by European and Japanese engineers. If a rock hurtles down a slope, a rockfall fence has to be strong enough to stop it—strong enough to absorb all the impact energy—but Wyllie says a better alternative may exist.

Rockfall and avalanche protection structures in BC include earth-filled berms ( top ) and walls ( middle ) , fencing, chain-net curtains, and sprayed shotcrete ( bottom ) . P hotos : top , B rian G ould , P.E ng ., middle and bottom , BC M inistry of T ransportation and I nfrastructure , via CC BY-NC-ND 2.0.

                                               

25

J AN UA R Y/ F E B R UA R Y 2 016

i n n o v a t i o n