Subsurface Engineering

How can the subsurface be explored to great depths?
How is an underground structure (e.g. tunnel, cavern) or a geotechnical structure (e.g. foundation, excavation pit) planned, designed and built?
How can the subsurface be used to produce or store energy?
How do subsurface materials (soil, rock) behave under different external actions?
How can the construction or operation of an underground structure be simulated on the computer?