Most tunnel boring machines are  normally around 17 metres in diameter.

大多数隧道掘进机的直径通常在 17 米左右。

And just a few years after that, in  2020, the company was using its own specialised tunnel boring machine to carry  out what is an unusually narrow excavation.

就在那之后的几年，也就是 2020 年，该公司使用自己的专用隧道掘进机进行异常狭窄的开挖。