It's applied to test minimum void ratio of non-cohesion
soil, whose granular diameter is no bigger than 5mm,
thus to provide data for relative density calculation.
Small metal barrel volumn: 250ml (dia48x13.9mm)
 Big metal barrel volumn: 1000ml
(dia100x127mm)
Hammer weight: 1.25kg
Drop: 15cm
Hammer foundation: diameter 50mm