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BOARD00469
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Last modified
8/16/2009 2:50:52 PM
Creation date
10/4/2006 6:39:03 AM
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Board Meetings
Board Meeting Date
5/12/1976
Description
Agenda or Table of Contents, Minutes, Resolution
Board Meetings - Doc Type
Meeting
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<br />I <br /> <br />I <br /> <br />structure. We have sixteen such structures. This.is pretty much <br />typical of the larger type. Now, these structures are located somewhat <br />upstream from the tunnel portal so that the water can b6! backed up and <br />diverted through feeder conduits to the downstream tunnel. We have <br />approximately twenty-six miles of tunnel and of that amount we have <br />driven about twenty-one miles. <br /> <br />I would like you to note that this is a typical drill blast and muck <br />operation, where a jumbo drill is moved in and the charges are set. <br />They are detonated and then the mucking machine goes in and pulls it <br />out. This iS,a shot of a jumbo drill, which pokes the holes so that <br />the charges can be set and detonated, and the mucking machine can come <br />in and pull it back over the top into the muck cars. If you have never <br />seen one of these things work, you are in for a real surprise. <br /> <br />It works on compressed air and the operator stands off to the side of <br />the car. And when he pulls the trigger, that thing slams into that <br />heading like nothing you've ever heard before and picks up loose muck. <br />The bucket is on the other side of the machine. It comes back up over <br />the muck machine and dumps into a muck car which is snubbed up very <br />closely to the back side of this machine. <br /> <br />(Slide) This shot shows the dumping of the muck cars. I believe this <br />was on the Nass Tunnel where the contractor had a pretty smooth and <br />efficient operation, where most of the cars were pulled out along the <br />waste disposal area and tipped and dumped. <br /> <br />(Slide) In some of our drill blast muck operations, we have used a <br />new technique known as "shot concrete" application. Very simply stated, <br />it's the introduction or spraying of concrete through about a three-inch <br />flexible tube with a nozzle on the end of it. As you can see, down in <br />the lower right hand corner of the screen, the tunnel set, the steel <br />set, the timber lagging and so forth are all encased in this "shot <br />concrete" as it's applied. It's applied in about three different <br />applications. Once it's complete, it has the appearance of - as near <br />as I can describe it - a textured ceiling. The concrete doesn't look <br />too solid. But the cores that I have seen are very, very strong and <br />solid. They are tested out for compressive strength very nearly as well <br />as concrete placed under more conventional methods. <br /> <br />Now, to draw a comparison, the Nass Tunnel was driven with a tunnel <br />boring machine. This particular machine was designed and built in <br />Germany and purchased by the Peter Kiewit Construction Company. The <br />cutter heads are of a very high strength, hard steel carbide type <br />material. The shoes that you see along the side going back along the <br />boring machine are forced out against the prism of the tunnel. This <br />thing is ten foot in diameter. It makes a hole that is perfectly round <br />so that when these shoes are forced out to the perimeter of the section, <br />they hold the machine in place and then, hydraulically, pressure is <br />applied against the cutter head. There is water injection at the <br />same time, and this cutter head rotates. The material so excavated is <br />brought off in a slurry. <br /> <br />If you will look at the top of the cutter head, you will see a little <br /> <br />-3- <br />
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