Vibro Systems were first developed in Germany in the 1930’s and make use of powerful depth vibrators to densify and reinforce soils in situ. The vibrators have an electric motor inside of them; and, unlike other installation systems that use a vibratory or impact hammer to drive a pipe, the energy and vibrations are applied directly in the hole, leading to very high rates of soil compaction even at wide spacings. Depending on soil types and the actual application, Vibro Systems can be referred to as Vibrocompaction, Vibroreplacement, stone columns or aggregate piers.
Vibrocompaction is used to densify loose sands and gravels by inserting the poker type vibrator into the ground with the aid of jetting water. A high degree of compaction is achieved through vibration and displacement of the soil. Sand may be added from the surface to maintain site elevation.
Vibroreplacement makes use of the same vibrator, but crushed rock or gravel is used to backfill the hole to form a Stone Column or Aggregate Pier. In this application the stone columns are installed using a dry, bottom feed system, where the crushed rock is fed to the tip of the vibrator using an internal feed pipe and compressed air. Excellent densification of granular soils is achieved, while at the same time constructing a stone column (aggregate pier) that provides reinforcement and settlement reduction.
Vibroreplacement stone columns are an ideal technique for mitigation of liquefaction because the system provides densification of liquefiable soils, reinforcement, and drainage. Vibroreplacement stone columns are also used on clays and silts to increase bearing capacity and reduce static settlement. The system can also be applied in very soft clays with high loads by injecting cement grout with the crushed rock to form Cemented Stone Columns.
Benefits of Vibro Systems
- Higher densification levels are achieved in granular soils relative to systems that use impact or vibratory hammers
- Utilize clean, crushed rock with a high angle of internal friction, resulting in high capacity aggregate piers
- Fast, economical system for mass ground improvement
- Can be installed near existing structures
- Progression of systems from Vibrocompaction to Vibroreplacement Stone Columns to Cemented Stone Columns