Английский язык. Жесткова М.В - 101 стр.

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101
ventilation. The only means of ventilating was the compressed air exhausted from the drills. It was so
insufficient that the death rate among the workers was extremely great. Needless to say that the
ventilation ought to have been much better.
a) What is the longest tunnel cut through the Alps? b) What was done to improve
ventilation in the course of tunneling? c) Why was a smaller bore (диаметр тоннеля)
adopted?
Both the Mont Cenus and the St. Gotthard tunnels are known to be single tunnels. But when it
was decided to bore the Simplon tunnel through the Alps, a different scheme was adopted because
geological conditions in this part of the mountains were not simple. The planned length of 12.3 miles
was greater than had been done before. According to the project two tunnels were cut, side by side,
with transverse galleries connecting them at certain intervals. In this way ventilation was greatly
improved and the removal of soil was made much easier. Each tunnel could take only one railway
track, so a smaller bore was adopted. Had the tunnel been made the same size as the earlier ones, it
might never have been completed. These arrangements made the construction much safer.
TEXT C
Read the text and translate it with a dictionary if necessary. Find out what caused the Tay
Bridge and the Tacoma Narrows Bridge disasters and what materials were used for constructing
bridges.
BRIDGE CONSTRUCTION
(1) The first bridges were all designed empirically, from the experience gained by previous
failures and successes. The history of bridge construction knows many examples when the bridges were
built without basic knowledge of Mathematics, which resulted in great tragedies. Engineering failures,
although often very costly in life and money, taught extremely valuable lessons.
(2) You must have heard of Tay Bridge disaster which took place at the end of the last century. The
Tay Bridge was designed by Thomas Bouch and opened in June 1878. It was two miles long and
spoken about as one of the wonders of the world. But unfortunately principles of aerodynamics
which should have been used in designing the bridge were yet unknown. So, the bridge was built
without any knowledge about the force a wind can exert on the bridge.
On Sunday afternoon, the 28
th
of December, 1879, a storm broke out at that place. By evening the
wind had reached the greatest force, and the people began to be nervous of what might happen to it in
such weather. Some of them went to the end of the bridge to await the arrival of the evening train from
Edinburgh. What they saw was a lighted train crossing the bridge. Suddenly the lights disappeared
as the engine and coaches fell into the water. All aboard the train were lost and it was difficult to
estimate the exact number of people, as some may have been carried out to sea.
(3) The Tacoma Narrows Bridge in the USA, which was the third longest bridge in the world, was
opened for traffic in July 1940. Owing to its behavior in wind, it was nicknamed «Galloping Gertie».
The deck of the bridge not only swayed sideways but large vertical waves appeared, and the roadway
oscillated up and down under the action of quite moderate winds. Drivers of cars reported that when
they crossed the bridge vehicles ahead of them completely disappeared from view and reappeared
several times, owing to the wavy motion of the roadway.
From the very beginning it was clear that the bridge structure ought to have been strengthened.
So, before the bridge was opened several attempts had been made to damp out [уменьшать
амплитуду] the oscillations of the main span. But they all were not a success. In November 1940, only
four months after the bridge was constructed, it collapsed under the action of wind of only 42 mph,
whereas generally bridges are designed to withstand winds of 120 mph.
(4) Early bridges had to be built out of material close at hand. In tropical jungles suspension
bridges were made of long bamboo poles. In the places where there were many forests it was wood. In
northern areas pier bridges were built out of stone. In Middle Ages people constructed wooden beam type
bridges. They were usually built on stone piers or wooden piles. Later, there appeared concrete and

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