2015-07-21
351
1. A tunnel is an underground (переход) produced by excavation or occasionally by an act of nature that dissolves soluble rock, such as limestone. A hillside tunnel (вход) is called a portal.
2. (Проходка тоннелей) is based on the high accuracy of underground geotechnical measurements called mine surveying. (Высокая отметка) must be correctly transmitted to the (ось тоннеля). The tunnel centre line must be correctly oriented in case of tunneling from both (портал).
3. Several additional (вертикальные стволы) are used to speed up tunneling when the tunnel has to be long. The tunnel is driven from these vertical shafts towards both entrances.
4. The New Austrian Tunnelling Method was developed in the 1960’s. The main idea is to use the geological stress of the surrounding (горная порода) mass to stabilize the tunnel itself. The (выработка) is immediately protected by thin shotcrete, just behind the excavation. This creates a natural load bearing (кольцо), which minimizes the rock’s deformation.
5. Pipe jacking is a method of tunnel construction where (гидравлический) jacks are used to push specially made pipes through the ground behind a tunnel boring machine or shield. This technique is commonly used to create tunnels under existing (cооружения), such as roads or railways.
6. In fact tunneling may have no notable problems, as long as the rock remains stable. However, the progress of an excavation may be slowed by a difficult (геологическая зона), which can turn out to be much longer than expected.
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