The kerf is the outside boundary of the tunnel wall that a boring machine gouges out as it bores through the ground or rock.

切口在隧道壁边界的外面，隧道壁是由钻机在钻透土地或岩石时挖出的。

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A subway construction worker, known as a "sandhog" exits the tunnel boring machine in the northbound tunnel of the Second Avenue subway construction project, Thursday, April 7, 2011 in New York.

2011年4月7日，纽约，被称作“沙狗”的隧道挖掘工人从第二大街地铁建筑工程的北向的隧道的隧道掘进机中走出。

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A full face rock tunnel boring machine was highly sensitive to geologic situation.

全断面岩石掘进机施工对地质地层状况非常敏感。

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Bureaucratic systems and processes were put in place to make the system tick over like a boring clockwork machine.

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