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Title: TUNNEL "DAYLIGHTING" ON THE ALASKA RAILROAD
Accession Number: 00468624
Record Type: Component
Availability: Find a library where document is available Abstract: In June 1984 routine scaling of loose rock from above the north portal of the 175-ft-long Tunnel 5 on the Alaska Railroad's Seward-Anchorage line revealed some large cracks and very unstable rock. Before stabilization work could be started, a 10-ft length of the tunnel collapsed, burying the track. Traffic was stopped for 48 hrs while the track was cleared and an assessment was made of stability conditions. In this paper are described the emergency procedures that were undertaken during the next month to correct the hazardous rock stability conditions in this area. The stabilization procedure consisted of blasting to daylight the 150-ft-long tunnel, thus forming a steep rock cut as much as 120 ft high. Because of the very unstable condition of the rock, it was necessary to remove the tunnel in a single blast consisting of about 600 holes. Most of the holes, with lengths of up to 80 ft, were drilled on the slope above the tunnel on a 6-ft-square pattern. Exceptions were the shear line holes, which were drilled on 2-ft centers, and two rows of holes drilled from the tunnel into the outside rib pillar. The holes were laid out in rows at 45 degrees to the track centerline and were detonated at 25-msec intervals using an electronic sequencer. The rib holes were detonated last in the sequence. The blast produced a stable face that required no stabilization and the total track closure time for loading and mucking was 50 hours.
Supplemental Notes: Publication of this paper sponsored by Committee on Engineering Geology. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
Monograph Title: Monograph Accession #: 01418086
Authors: Weeks, F CTrueblood, T BKrause, AWyllie, D CPagination: pp 115-118
Publication Date: 1987
Serial: ISBN: 0309044723
Media Type: Print
Features: Figures
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; Maps
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; Photos
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TRT Terms: Identifier Terms: Uncontrolled Terms: Geographic Terms: Old TRIS Terms: Subject Areas: Bridges and other structures; Construction; Design; Geotechnology; Highways; Public Transportation; I25: Design of Tunnels; I43: Rock Mechanics; I54: Construction of Tunnels
Files: TRIS, TRB, ATRI
Created Date: May 31 1988 12:00AM
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