Vibro Concrete Columns
Vibro concrete columns (VCCs) are an effective ground improvement technique developed to provide integrity through weak organic soils or to provide greater settlement control than can be achieved with vibro stone columns.
How the technique works
A vibroflot is lowered into the ground and penetrates through the soil under its own mass, vibration, and air flush. When it reaches design depth concrete is poured from the tip of the vibroflot via an adjacent tremie pipe, which is attached to a concrete pump. The vibroflot is lowered again to the required depth to compact the infill and interlock it tightly with the surrounding soil. The cycle is repeated until a compact concrete column is constructed up to ground level.
Typically concrete columns are 400mm in diameter with an enlarged 600mm diameter base. The column diameter varies with the soil conditions, but generally the weaker the soils, the larger the diameter of the concrete column required.
The spacing and arrangements of the concrete columns are dependent on the soil conditions and the loads carried by the foundations.
VCCs are ideal:
- On contaminated piling sites where spoil removal is to be avoided, i.e. for regeneration of brownfield sites
- Where peat and organic soils preclude conventional vibro techniques
- Where founding at a high level is required to avoid piling into an aquifer
- Where short construction programmes dictate fast-track installation & high production levels
- For loads/settlement control with a load transfer platform
