test pit; pilot tunnel
Technical term in mining, civil engineering, and geology for a small excavation or borehole made to investigate ground conditions.
Before tunnel construction, they dug a test pit to investigate the geology.
From the test pit survey results, it was found that this location has soft ground.
試掘 (test excavation) is the general act of digging to investigate; 試掘坑 specifically refers to the pit or tunnel itself.
Boring survey is a more common term for drilling-based ground investigation, while 試掘坑 often implies a larger excavated opening.
Standard kanji form using 坑 (pit/tunnel).
Variant using 孔 (hole/borehole); less common but seen in geological contexts.
Compound of 試 (test) + 掘 (dig) + 坑 (pit/tunnel). A straightforward technical term formed from Sino-Japanese morphemes.