Stone column construction should be closely monitored and design adapted to suit actual soil conditions. The shear stress is partially taken over by the stone column Stone columns reinforce and compact the soil. Liquefaction can be prevented.
The design comprises the assessment of bearing capacity, settlement, stability and liquefaction potential of a soil after Vibroflotation Ground Improvement.
For Vibro Compaction the design is very straightforward : Assess the required improved soil strength and stiffness after compaction and calculate otherwise as for any unimproved soil. The only difficulty lies in the evaluation of the degree of compaction possible in different soils. This can only be assessed with extensive experience in local soil conditions and the use of appropriate sounding techniques. For stone columns the design is much more complex. Stone columns are a ground reinforcement, and their behavior is closely linked to the behavior of the soil surrounding the columns. Specific calculation methods for stone columns have been developed and calibrated using full scale tests, allowing stone columns to be designed with the same confidence as piles but with the advantage of better resistance to earthquake loads.