167. Read the text and put the verbs in the correct forms. Translate in writing.

Underground chambers, often (assosiate) with a complex of (connect) tunnels and shafts, are increasingly (use) for such things as underground hydroelectric-power plants, ore-prossesing plants, pumping stations, vehicle parking, storage of oil and water, water-treatment plants, warehouses, shoping complexes, and light manufacturing; underground chambers also (use) as command centres and other special military needs. A hillside tunnel entrance is (call) a portal; tunnels may also (start) from the bottom of a vertical shift or from the end of a horizontal tunnel (drive) principally for construction access and called an adit.

References: http://www.wisegeek.com/what-is-the-channel-tunnel.htm

UNIT 5. DESIGN AND CONSTRUCTION METHODS.

Vocabulary.

inward pressure – внутреннее давление

outward pressure – наружное давление

rectangle – прямоугольник

weak point – слабое место

flat – плоская поверхность

volume – объем

sample – образец

water supply system – система водоснабжения

tunnel shield – туннельный щит

contraption – устройство

tunnel boring machine – штрекобурильная машина

soft–ground –сыпучая порода, рыхлый грунт

hard rock– твёрдый грунт

gushing – фонтанирование

quarry – карьер

stable – стабильный

reliable – надежный

structurally sound – герметичный

shallow – мелкий

enormous – огромный

prefabricated – сборный

firm – твердый

complicated – сложный

to wonder – интересоваться

to distribute – распространяться

to investigate – исследовать

to prevent –предотвратить

to collapse –обрушаться

to force – вынудить

to blast – взорвать

to rely on – полагаться

to attach – прикреплять

to fit – соответствовать

afterwards – впоследствии

evenly/equally – равномерно / одинаково

Why are tunnels round? People Tunneling or digging a shaft is not very particular about the shape of their tunnels or shafts. Tunnels or shafts should be round. Ever wondered why pipes are round, so do submarines, road tunnels or tunnels for trains or even planes. Inward pressures or outward pressures have got a lot to do with it. More exactly, in architectural design and building tunnels and shafts, the most efficient shape is a circle because it means the outside pressure in evenly/equally distributed while a rectangle shape has weak points. Horizontal tunnels are mostly designed in a "parabolic shape" with a flat base. One probable reason is to minimize the volume of soil, stones, and other solid materials being extracted out during the digging operation of the tunnel.

Before carving a tunnel, engineers investigate ground conditions by analyzing soil and rock samples and drilling test holes. Based on the setting, tunnels can be divided into three major types:

1. Soft-ground tunnels are typically shallow and are often used as subways, water supply systems, and sewers. Because the ground is soft, a support structure, called a tunnel shield, must be used at the head of the tunnel to prevent it from collapsing.

2. Rock tunnels require little or no extra support during construction and are often used as railways or roadways through mountains. Years ago, engineers were forced to blast through mountains with dynamite. Today they rely on enormous rock-chewing contraptions called tunnel boring machines.

3. Underwater tunnels are particularly tricky to construct, as water must be held back while the tunnel is being built. Early engineers used pressurized excavation chambers to prevent water from gushing into tunnels. Today, prefabricated tunnel segment is sunk, and attached to other sections.

There are three steps to a tunnel’s success. Today, engineers know that there are three basic steps to building a stable tunnel. The first step is excavation: engineers dig through the earth with a reliable tool or technique. The second step is support: engineers must support any unstable ground around them while they dig. The final step is lining: engineers add the final touches, like the roadway and lights, when the tunnel is structurally sound.

Building a tunnel through anything is a slow process that involves excavation by digging, blasting or boring into rock. Tunnels are dug in different kinds of grounds, from soft sand to hard rock. The way of digging is chosen by the type of ground. There are two additional ways of digging: quarry and “cut and cover”. In quarry, the tunnel path is drilled in a horizontal way. This system requires a deep tunnel that is built in a firm rock. In the “cut and cover” system, a tunnel is dug in the ground and afterwards a roof is built above the tunnel. This system fits tunnels that are close to the ground like road tunnels and infrastructure.

Planning a tunnel is complicated, and it uses science and mathematics. The way a tunnel is built depends on what material the tunnel has to go through. Building tunnels is a large civil engineering project that could cost very high sums of money. The planning and building of a long tunnel may take many years.

Answer the questions to the text.

1. Why are tunnels round?

647. What do engineers do before carving a tunnel?

648. What are 3 major types of tunnels? Speak of them.

649. What steps are there to a tunnel’s success?

650. What kinds of grounds are the tunnels dug in?

651. Describe two additional ways of digging: quarry and “cut and cover”.

652. Why is tunneling considered to be a large civil engineering project?

Exercises: