Ice Tunnel Closure Phenomena PDF Download
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Author: John F. Abel
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages : 56
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Book Description
The mechanics of closure, exhibited by ice tunnels, can be understood by considering the ice as a viscous solid. The viscous solid will flow, when subjected to a force, at a rate dependent on the magnitude of the force, the area of relief open for flow, and the apparent viscosity of the viscous solid. In the case of the ice tunnels, the force inducing the flow is the weight of the overburden; the area of relief open for flow is the tunnel opening; and apparent viscosity is the resistance to flow exhibited by the ice. The closure of a rectangular opening made in ice was measured. Maximum closure occurs at the center of unsupported roof, wall, or floor spans. The vertical closure rate decreases negligibly approximately 2% from the center of a room to approximately 6 ft from the wall. From the point about 6 ft from the wall to the wall, the closure rate decreases about 30%. Approximately 30% of vertical closure at the center of the span is due to flexure of the floor and roof. The remaining 70% is due to shortening of the wall height; the major portion of this wall closure occurs at the bottom of the wall. Over 80% of closure due to flexure of the floor and roof results from flexure of the floor. (Author).
Author: John F. Abel
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages : 56
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Book Description
The mechanics of closure, exhibited by ice tunnels, can be understood by considering the ice as a viscous solid. The viscous solid will flow, when subjected to a force, at a rate dependent on the magnitude of the force, the area of relief open for flow, and the apparent viscosity of the viscous solid. In the case of the ice tunnels, the force inducing the flow is the weight of the overburden; the area of relief open for flow is the tunnel opening; and apparent viscosity is the resistance to flow exhibited by the ice. The closure of a rectangular opening made in ice was measured. Maximum closure occurs at the center of unsupported roof, wall, or floor spans. The vertical closure rate decreases negligibly approximately 2% from the center of a room to approximately 6 ft from the wall. From the point about 6 ft from the wall to the wall, the closure rate decreases about 30%. Approximately 30% of vertical closure at the center of the span is due to flexure of the floor and roof. The remaining 70% is due to shortening of the wall height; the major portion of this wall closure occurs at the bottom of the wall. Over 80% of closure due to flexure of the floor and roof results from flexure of the floor. (Author).
Author: Paul Bierman
Publisher: W. W. Norton & Company
ISBN: 1324020687
Category : Science
Languages : en
Pages : 179
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Book Description
Paul Bierman’s realization that Greenland’s ice sheet melted when Earth was no warmer than today sounds an alarm for our planet. In 2018, lumps of frozen soil, collected from the bottom of the world’s first deep ice core and lost for decades, reappeared in Denmark. When geologist Paul Bierman and his team first melted a piece of this unique material, they were shocked to find perfectly preserved leaves, twigs, and moss. That observation led them to a startling discovery: Greenland’s ice sheet had melted naturally before, about 400,000 years ago. The remote island’s ice was far more fragile than scientists had realized—unstable even without human interference. In When the Ice Is Gone, Bierman traces the story of this extraordinary finding, revealing how it radically changes our understanding of the Earth and its climate. A longtime researcher in Greenland, he begins with a brief history of the island, both human and geological, explaining how over the last century scientists have learned to read the historical record in ice, deciphering when volcanoes exploded and humans started driving cars fueled by leaded gasoline. For the origins of ice coring, Bierman brings us to Camp Century, a U.S. military base built inside Greenland’s ice sheet, where engineers first drilled through mile-thick ice and into the frozen soil beneath. Decades later, a few feet of that long-frozen earth would reveal its secrets—ancient warmth and melted ice. Changes in Greenland reverberate around the world, with ice melting high in the arctic affecting people everywhere. Bierman explores how losing Greenland’s ice will catalyze devastating events if we don’t change course and address climate change now.
Author: Cold Regions Research and Engineering Laboratory (U.S.)
Publisher:
ISBN:
Category : Frozen ground
Languages : en
Pages : 28
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Author: John F. Abel
Publisher:
ISBN:
Category : Ice tunneling
Languages : en
Pages : 86
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Book Description
Methods of excavating in the Greenland Ice Cap, and the planning required, equipment employed, and problems encountered are described individually for each of 5 operating seasons (1955-1959), and relative cost evaluations of the different methods are given. Three basic methods were used: hand-picking and manual haulage; explosives and manual haulage (drill-blast-muck cycle); and mechanized mining and haulage. Manual methods, which are of low capacity and limited to widths under 12 ft, are justified only when small openings are required, and in remote, inaccessible regions. The drill-blast-muck cycle of mining has a slightly higher capacity than manual methods, but requires power to operate the drills and to ventilate after blasting. Explosives can be used for room spans not exceeding 12 ft; when greater spans are excavated by blasting, the resulting roof is unstable. The machine method using mechanized coal mining equipment has the highest capacity and the lowest unit cost. Openings with roof spans in excess of 36 ft have been made with coal mining machines without dangerous roof conditions developing.
Author: Cold Regions Research and Engineering Laboratory (U.S.)
Publisher:
ISBN:
Category : Arctic regions
Languages : en
Pages : 478
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Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1990
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Author:
Publisher:
ISBN:
Category : Geology
Languages : en
Pages : 700
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Book Description
1919/28 cumulation includes material previously issued in the 1919/20-1935/36 issues and also material not published separately for 1927/28. 1929/39 cumulation includes material previously issued in the 1929/30-1935/36 issues and also material for 1937-39 not published separately.
Author:
Publisher:
ISBN:
Category : Earth sciences
Languages : en
Pages : 904
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Author: United States. Superintendent of Documents
Publisher:
ISBN:
Category : United States
Languages : en
Pages : 1250
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Author: United States. Superintendent of Documents
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1248
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