field·work /ˈfi(ə)lˌdwɚ/
野戰工事,野外工作
Field·work n. Mil. Any temporary fortification thrown up by an army in the field; -- commonly in the plural.
All works which do not come under the head of permanent fortification are called fieldworks. --Wilhelm.
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fieldwork
n : a temporary fortification built by troops in the field