The vibro hammer is frequently used in the oil and gas industry to install jacket piles in combination with an impact hammer. The reason for using the vibro here is to use it to position the pile and then to drive it until it is stable before the impact hammer is placed. This mitigates the risk of the jacket or template toppling over due to the leaning pile, particularly when a heavy impact hammer is placed. This way a relatively small vibro can be used to position and stabilise a pile before a large impact hammer is placed.
The risk of "Free Pile run" is also an important reason for choosing a vibro hammer in high risk soft soils. First of all the risk of free pile run is already mitigated as there are no sudden bursts of energy released into the pile and secondly as the pile is fixed to the vibro, the pile can't "run".