Added to this that a tunnel would have to be about 50 km long and that the removal of earth would require a fleet of trucks etc it is liable to detection.

此外，一条长达50公里的隧道必然要挖出大量的土方，需要大量的卡车装载运出，诸如此类的事件都使得隧道很容易被发现。

youdao

Unless there is a bridge, tunnel, or other special structure, this roadbed is constructed of in-situ soils or on earth embankments.

只要没有桥、隧道或其他特殊建筑，路基就可以建在土堤上。

youdao

Based on model comparison between the semi-infinite earth and the circular tunnel with peripheral infinite earth, the conception of long and large tunnel in the electrical meaning is put forward.

在比较半无限平面大地模型和四周无限大地圆形隧道模型基础上，提出电气上的长大隧道概念。

youdao

In spite of round-the-clock work, progress on boring a huge tunnel into the earth was not up to mark.

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