Stone Columns (SC) are formed with specially designed vibroflot mounted on a base machine. Formation is executed in three basic phases:
- inserting the vibroflot into the ground up to the design depth: the process is often assisted by injecting compressed air, water or air-water mix,
- aggregate backfill
- compacting with vibroflot, in stages by adding the aggregate at every 0.5 m.
Aggregates used for column forming:
- multigrain natural aggregates (gravel, sandy gravel and crushed-stone aggregate),
- silt fraction below 5%,
- supplied via a feeding pipe connected to the vibroflot (dry bottom feed) or from the level of the working platform along the vibroflot (wet top feed) – depending on the method.
The Stone Column technology is well suited for the improvement of firm and soft soils (silts, sandy silts, loams and non-homogeneous soils) as well as non-cohesive soils where enhanced properties are needed.
Vibroflotation columns lead to global improvement of the soil parameters, resulting in substantial reduction of complete and differential subsidences. In addition, after installation the columns can fulfill drainage role.
The Stone Columns are successfully used for:
- Foundations of enclosed buildings (warehouses, shopping malls, residential buildings),
- Floors of industrial buildings,
- Railway and Roadway Embankments,
- and more.
At surface strengthening, the columns are arranged in a square or triangular grid with a spacing ranging from 1.5 m to 3.0 m so that the soil replacement factor is within the range from 15% to 35%.
- High bearing capacity – high shear strength and low deformation capacity of columns formed in weak soil.
- Strenghtening in a global scale: improving mechanical properties of the soil found between the columns, displacement/densification of the soil between columns, drainage function of the colums (quicker consolidation time);
- Environmentally friendly: the columns can be formed from recycled material (crushed concrete, etc);
- High efficiency: even more than 200 meters of columns per shift (when using single equipment unit);
- No excavated material.