Vibro Stone Column

Summary

Vibro Stone Column - A vibro stone column is a type pile formed from graded aggregates; used to diminish settlement and increase bearing capacity of a soft soil.

Technical Information

A vibro stone column can be a much more economical and sustainable alternative to standard piling. The selection of this type of ground improvement will follow on from the Geotechnical Engineers testing and investigations and will be to their design.

The aggregate used will have a low compressibility and a higher bearing capacity relative to the surrounding soil. Also the large voids between the aggregate particles create a drainage path dissipating the water faster, than the soil, in turn reducing settlement time.

There are two ways these stone columns can be created: via a top feed process (more conventional) or bottom feed process.

Top Feed: a vibrator column penetrates a weak soil down till design depth, densifying the soil around the perimeter of the cavity. It will then be raised and an excavator will pour aggregate into the cavity. Once a portion is filled, the vibrator is then pushed down again to compress the portion of aggregate. This process is repeated in stages till the aggregate column reaches the surface.
Bottom Feed: the exact same process, but the vibrator has a second hollow column running down it for the aggregate to pass down; this results in the aggregate being fed directly to the bottom of the cavity. Used in weaker soils or soils with higher water tables, as this method ensures the integrity of the column.

The following process can be used in conjunction with either of the above:

Wet Feed: this entails the addition of a water jet spraying from the bottom of the vibrating column, which is used where silts and fine particles are present. This jet helps remove fine and loose materials to form the cavity.

Recycled aggregates can also be used, to increase sustainability of the project.