挖掘 

Pinyin: wā jué
Meaning：Excavation 
Sentence：我们需要一台挖掘机来平整土地。We need a mechanical digger to level the ground.

More: 

挖： 

Pinyin: wā
Meaning: to dig
Radical: 扌
Stokes: 9
Traditional: 挖
Common words/Phrase:
挖苦[wā kǔ] 【persiflage】 
挖洞[wā dòng] 【cave】
挖方[wā fāng] 【cubage of excavation】

掘： 

Pinyin: jué
Meaning: Dig
Radical: 扌
Stokes: 11
Traditional: 掘
Common words/Phrase:
掘进[jué jìn] 【tunnelling】
掘墓人[jué mù rén] 【grave-digger】
掘墓[jué mù] 【to exhume】