Engineering Wonders of the World
Volume I
Forfatter: Archibald Williams
År: 1945
Serie: Engineering Wonders of the World
Forlag: Thomas Nelson and Sons
Sted: London, Edinburgh, Dublin and New York
Sider: 456
UDK: 600 eng - gl.
Volume I with 520 Illustrations, Maps and Diagrams
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60
ENGINEERING WONDERS OF THE WORLD.
work. However, fourteen weeks sufficed to
bring the pilot tunnel to within 60 yards of
No. 2 Shaft, and a small timbered heading
was driven for the remainder of the distance.
The pressure of the compressed air was regu-
lated to suit the tide in the river, being highest
of bubbles, but very little water came into
the tunnel.
As soon as the pilot tunnel was stopped,
preparations for starting the main tunnel were
at once hurried forward, and the shield, the
most important of all the special appliances
THE TUNNEL ON CURVE.
at high-water, when it averaged about 20
lbs. per square inch, and falling to 14
lbs. per square inch at low water. The
materials met with were sandy clay, shells,
sand, and the rock already mentioned. There
was a small escape of compressed air, which
showed itself in the river above in the form
used, was got ready for work. A shield has
been employed in the construction of all the
tunnels under the river Thames, including the
original Thames Tunnel.
The design adopted was very similar to that
used in other large tunnels, but larger and
heavier than any previously constructed. It