For a long time, they used percussion drilling - which basically means they hammered away at the ground to get as deep as they could get.

很长时间里他们用冲击钻井——基本上就是不停地砸地面，直到砸不动。

youdao

For a long time, they used percussion drilling - which basically means they hammered away at the ground to get as deep as they could get.

很长时间里他们用冲击钻井——基本上就是不停地砸地面，直到砸不动。

youdao