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Stone Columns FAQ
Vibroreplacement/Vibrodisplacement


What soil types can be improved by stone columns?

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Stone columns can be used for any soil type, however, for clean sands and gravels, there is generally no need to use a stone backfill since conventional vibrocompaction works well.



Are vibrations a problem for neighboring structures?

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As with conventional vibrocompaction, vibrations are generally not a problem.



What is the difference between vibro-displacement and vibro-replacement?

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With vibro-replacement, the hole is created by jetting, either with water or air.  Stone is then added and compacted with the vibroflot.  With vibro-displacement, the hole is created by forcing the vibroflot into the ground, displacing the soil horizontally (without trying to jet any material out).  Stone is then added and compacted by the vibroflot in the same manner as with vibro-replacement.



Are there any technical advantages or disadvantages between vibro-replacement and vibro-displacement?

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When using vibro-displacement in cohesive soils, it is possible to remold the soil and cause a loss of preconsolidation pressure.  It is therefore important to evaluate whether this condition can occur in the engineering design phase of the project.



Can you install stone columns below the water table?

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Yes, as with vibrocompaction, stone columns can be used on soils below the water table.



Do you have to use water jetting?

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Either jetting with air or jetting with water are required, unless the holes are predrilled.



How much improvement is possible?

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Generally, stone columns reduce the compressibility of soft materials by a factor of 2 to 5, depending on the spacing and diameter of the columns and the stiffness and type of the matrix soils..