I-90/雪地到Keechelus Dam阶段1C项目
Hyak, Wash.
最佳项目，高速公路/桥梁以及优异的奖项，卓越的安全性
Key Players
所有者华盛顿州运输部
Lead Design Firm雅各布斯
Contractor盖伊·F·阿特金森建筑
GeotechnicalDesign Geoengineers
分包商KLB Construction; Golder Associates Inc.; HI-TECH Rockfall Construction Inc.
在华盛顿州运输部授予合同后，立即通过Snoqualmie Pass扩大了2.89英里的90英里处，Guy F. Atkinson Construction提出了一项降低成本的激励提案，以将WSDOT寻求的雪地保护驾驶员免受雪崩的保护。进入双胞胎1,200英尺长的雪崩桥。
Elevating the bridges eliminated the need for a snowshed, raising the three lanes of roadway in each direction above avalanche potential, shoehorning the structures into a mountain pass between an avalanche-prone rock cliff and environmentally sensitive lake. At the same time, the project’s design created a structure able to withstand seismic, landslide and avalanche loads; widened the roadway; and saved WSDOT more than $37 million in long-term maintenance from avalanche removal. Plus, the bridges offered a safer construction method than erecting a new snowshed.
“We were able to come in and save WashDot a bunch of future monies through doing this,” says Philip Larson, Atkinson project manager. “It gave us a great chance to partner with WashDot to train a whole bunch of staff on new construction techniques. When we walked out, we were more of construction professionals than when we started. It was a really fun job.”
这项耗资6300万美元的九年项目始于桥梁的变化，从而构成了设计挑战。在北美的三位雪崩专家中，有两名已经与WSDOT合作，而阿特金森（Atkinson）提出了第三名，以帮助确定可接受的风险耐受性。在大多数在瑞士或北美，科罗拉多州进行的雪崩研究中，需要额外的工作来确定湿太平洋西北雪的正确标准，通常比其他地方重达四倍，较慢。
然后是在容易行动的山悬崖和基切鲁斯湖之间工作的复杂性。每年冬天，团队都计划下个赛季的工作。拉尔森说：“您希望自己的计划正确，然后推动天气窗口。”“那是我们每年秋天玩了八年的游戏，安全地工作得多。”
“You hoped your plan was correct, and then you pushed the weather window. That was a game we played every fall for eight years, how late to work safely.”
– Philip Larson, Project Manager, Guy F. Atkinson Construction
The trickiest part of the construction came with nightly rock blasting for five years straight, but only after the eastbound bridge was constructed. Atkinson selected blasting techniques to limit ground accelerations and reduce the potential for damaging the completed bridge. “The rock up there was very incompetent and very weathered with a lot of veins,” he says. “Every time you blasted you never knew what would happen. That constant fear of that rock not acting as it was supposed to every night, that was not standard to me.”
Rock blasting was the only solution to make room for the interstate widening, requiring precautions all around. Atkinson limited how much it blasted at one time, and automated stations across the slope ensured the hillside wasn’t moving, with checks after each blast. “It worked,” Larson says. “No one got hurt, and there were no major slides.”
桥梁的对齐需要清除积雪，但并不是那么高，以至于在冰冷条件下成绩变得危险。桥墩也必须支撑桥梁，但承受并发的雪崩和滑坡的力量，同时为跌落的岩石提供了空间，可以错过道路，但不会靠近湖泊，这太深了，无法支撑地基。
最终的结果教会了工作人员如何克服挑战，为驾驶员提供了备受改善的道路，并节省了WSDOT的时间和金钱，在雪崩控制中，没有通过不关闭华盛顿各地的东方主要链接来计算经济和公共服务节省。
WSDOT Avalanche预报员和控制团队主管John Stimberis说：“除非出现非常具体的条件，否则我认为不需要在桥梁地点执行任何雪崩控制。”“由于雪崩桥已经到位，我们已经录制了22种自然发生的雪崩，到达了旧路基。如果雪雪仍然到位，我估计自雪崩桥梁完成以来，我们将执行近50次雪崩控制任务。”
