Stone columns

Soil improvement by means of stone columns results in the construction of cylindrical elements, cast-in-situ, consisting of gravel that is compacted by driving, or by using vibroflotation (vibro-compaction).

Construction chart

Construction sequence

Installation process of a stone column by bottom driving with an internal ram.

1. Construction of a gravel plug at the bottom of the cylindrical steel casing

2. Bottom driving on the plug using an internal ram (piston) causes the casing to be driven into the soil, down to the required founding level, and displace the surrounding soil laterally.

3. When the required installation depth of the column has been reached, expulsion of the plug with the cylindrical internal piston.

4. Realisation of the compacted stone column, formed by adding and expelling the required amount of gravel while simultaneously and gradually withdrawing the tube.

5. Completed gravel column

Fields of application

• Economical solution for foundations under constructions with uniformly distributed surface loads (up to 50 kN/m2) resulting in the reduction of settlements: industrial warehouses, reservoirs, storage facilities such as tanks and silos, pipelines and sewers

• Fast consolidation of backfills and embankments.

Environmental impact

• Little vibrations

• No removal of soil

• A stable, dry and flat work platform is required

• Heave of the soil.

Technical specifications

• Diameter varying from 600 up to 800 mm

• Soil improvement by the insertion of stone columns on a regular grid spacing.

• Improvement of the soil mechanical characteristics of soft and / or compressible layers of soil by the insertion of compacted and laterally displaced granular material (gravel).

• By closer monitoring of the installation process and a higher compaction energy by lateral soil displacement during the driving phase, stone columns have - unlike stone columns compacted by means of vibroflotation - a higher bearing capacity and a better settlement behaviour.

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