It is difficult to dig the ground when it is frozen hard 地面冻硬时不易挖掘。
She used a spade , which you use to dig the ground . she dug it up and it fell ; and she dug it up again and it fell again . i said , " no , you cannot do that . 她用一支你们用来挖土的那种铲子去挖它,她把它挖起来,它就掉下去,她又挖起来,它又掉下去,我说:不行!
As an unexcavtion technology , pipe jacking have an unique excellence for it need not dig the ground surface . so it have been used widely in civil engineering 顶管法作为非开挖的技术中的一种,可以在不用开挖地表土的情况下将管道铺设完毕,具有无可比拟的优点,其应用也越来越广泛。