A vibro-pile is a closed off casing that is vibrated into the ground displacing and "densifying" all the material in its path. The casing is then filled with concrete and reinforcement and then extracted (or filled with concrete as it is extracted and the reinforcement is installed later.)
Vibro-pile is used as an alternative to pre-cast piles or drilled cast-in-situ piles in soft grounds especially when vibrating a can/probe is faster than drilling and casing or when vertical tie downs are necessary.
The multi-purpose ABI Mobilram is the ideal piece of equipment for vibro-pile applications. More information on the Mobilram.