Mixed and fine-grain soils frequently have an insufficient bearing capacity and stiffness. Should the fine grain share be around 5% higher, an adequate self-compaction is no longer to be expected. This is where the vibro replacement compacting comes into question as an improvement. This process is also suitable for the improvement of coarse-grain backfills comprising rubble, slag or overburden.
A special area of application are vibro drain columns. Flotation is dispensed with hereby. The column then merely acts as a drain.
The vibro replacement
In most cases, a bottom feed vibrator is used, with which a coarse-grain fill material is discharged at the tip of the vibrator with compressed air support. The vibrocats with a leader that have been designed by Keller provide an additional pull-down pressure to be applied when the vibrator is being lowered and is compacting.
In vibro replacement compacting, the work is carried out in alternate steps. The gravel or crushed stones that are discharged from the vibrator hub are compacted and displaced into the soil at the side. This results in the formation of replacement columns that bear the loads in connection with the soil. The creation parameters are digitally recorded in the device.
Benefits of the vibro replacement compaction
- no inclusion in the bearing soil
- normally no soil transportation (important with regard to polluted soils)
- especially economical dimensioning of foundations and floor slabs
Information for design and execution
In foundation terms, a soil that has been improved by means of vibro replacement compaction can be treated in the same way as normal adequately load-bearing and deformation resistant foundation soil.