Review of Underground Tunneling Techniques at the New Irvington Tunnel in San Francisco, California and the Virginia and Truckee Railroad in Virginia City, Nevada
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Authors
McManus, Shelby
Issue Date
2012
Type
Thesis
Language
en_US
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Abstract
The Irvington Tunnel located beneath San Francisco, California transports drinking water
from Hetch Hetchy Reservoir to almost 2.5 million people. Due to seismic activity concerns and
lack of renovation, portions of the tunnel are being replaced. The New Irvington Tunnel project
is currently underway; tunneling mechanisms include blasting and traditional mining techniques.
However, support after excavation is not widely known. Research on tunneling through weak
rock masses was conducted in Virginia City, Nevada in order to determine the best practices for
support of deep tunnels. The Virginia and Truckee Railroad company has one tunnel that has had
multiple failures since the 1950s. This tunnel, Tunnel 3, was visited to collect data and determine
the cause of failure. The Tunnel is located in moderately to highly altered Alta Formation
andesite and has silty clay surrounding its failure zone. The west side of the tunnel has a blocky
joint condition with the joints crossing each other. The joint orientations on the east side are
parallel to each other and the material is of a higher degree of alteration. This is assumed to be
the cause of failure on the east end of Tunnel 3. The properties of the weak rock at Tunnel 3
were used to create strength and displacement finite element models for a deep tunnel. This is
related to the New Irvington Tunnel and shows that multiple supports are needed, such as rock
bolts, infill, and composite liners, to avoid failure.
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In Copyright(All Rights Reserved)