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英语翻译
After the general dirction for a tunnel has been determined,the next steps are a geological survey of the site and a series of borings to obtain specific information on the strata through which the tunnel may pass.The length and cross section of a tunnel generally are governed by the use for which it is intended ,but its shape must be designed to provide the best resistance to internal and external forces.Generally,a circular or nearly circular shape is chosen.
In very hard rock,excavation usually is accomplished by drilling and blasting.In soft to medium-hard rock,a tunnel-boring machine typically does the excavating work.In soft ground,excavation usually is accomplished by digging or by advancing a shield and squeezing the soft material into the tunnel.In all cases the excavated rock or earth,called muck,is collected and transported out of the tunnel.In underwater tunneling,a shield is used to advance the work.Another method of building an underwater tunnel is to sink tubular sections into a trench dug at the bottom of a river or other body of water.
After the general dirction for a tunnel has been determined,the next steps are a geological survey of the site and a series of borings to obtain specific information on the strata through which the tunnel may pass.The length and cross section of a tunnel generally are governed by the use for which it is intended ,but its shape must be designed to provide the best resistance to internal and external forces.Generally,a circular or nearly circular shape is chosen.
In very hard rock,excavation usually is accomplished by drilling and blasting.In soft to medium-hard rock,a tunnel-boring machine typically does the excavating work.In soft ground,excavation usually is accomplished by digging or by advancing a shield and squeezing the soft material into the tunnel.In all cases the excavated rock or earth,called muck,is collected and transported out of the tunnel.In underwater tunneling,a shield is used to advance the work.Another method of building an underwater tunnel is to sink tubular sections into a trench dug at the bottom of a river or other body of water.
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