Vibro Replacement (Stone Columns)

Vibro replacement is a ground improvement technique that constructs dense aggregate columns (stone columns) by means of a crane-suspended downhole vibrator, to reinforce all soils and densify granular soils. Vibro replacement stone columns are constructed with either the wet top feed process, or the dry bottom feed process.

In the wet top feed process, the vibrator penetrates to the design depth by means of the vibrator’s weight and vibrations, as well as water jets located in the vibrator’s tip. The stone (crushed stone or recycled concrete) is then introduced at the ground surface to the annular space around the vibrator created by the jetting water. The stone falls through the annular space to the vibrator tip, and fills the void created as the vibrator is lifted several feet. The vibrator is lowered, densifying and displacing the underlying stone. The vibro replacement process is repeated until a dense stone column is constructed to the ground surface.
 
The dry bottom feed process is similar except that no water jets are used and the stone is fed to the vibrator tip through a feed pipe attached to the vibrator. Predrilling of dense strata at the column location may be required for the vibrator to penetrate to the design depth. Both methods of construction create a high modulus stone column that reinforces the treatment zone and densifies surrounding granular soils.

Vibro replacement stone columns have been used to increase bearing capacity, and decrease settlement and mitigate liquefaction potential for all types of planned structures including buildings, embankments, dams, tanks and towers.

Vibro replacement rigs can be fully instrumented with an on-board computer to monitor specific parameters. Monitoring these parameters allows the operator to correct any deviations in real-time during the construction process to keep the stone column within project specifications.  Data from the Data Acquisition (DAQ) system such as amperage and lift rate are recorded and displayed in real-time alongside specified target values on an in-cab monitor.

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