лучшего пока не нашел. встретилось пару раз:
Foundation: all works below ground level

Type of works below ground level Distance5
Trench or other excavation works in stable ground conditions up to 1.5 metres in depth 3 metres
Trench or other excavation works in stable ground conditions over 1.5 metres and up to 5 metres in depth 5 metres
Trench or other excavation works in stable ground conditions over 5 metres in depth 10 metres
Vertical penetration including sheet piling, ground investigation and any kind of drilling or core sampling or ramming 3 metres
Welding or other hot works near exposed U/G cables 10 metres
H-Piling, percussion moling or pipe jacking 15 metres
Any form of tunnelling, boring, construction of caverns, driving headings, cable jacking
always consult electricity supplier
Use of explosives 60 metres

по моему earthworks - это ближе к excavation и не очень отражает то, что в этом вопросе задано - работы по строительству структур ниже уровня земли. приведенное - возможно, не лучший вариант, но "к истине чуть ближе"