Soft Ground Improvement with Geosynthetic Encased Column(s)

Stone columns are widely used for improving soft ground, with the principle of replacing unfavourable in-situ soft deposit. The application alone, however, shows limitations in provision of sufficient load bearing capacity due to low lateral soil confinement, when installed in extremely soft soil; consequently, the stone columns are likely to undergo excessive bulging which adversely affects not only the structural integrity, but also the drainage capacity as the soft deposit tends to flow in and eventually fill up the voids of the stone aggregates. The limitations can be overcome by encasing stone columns with geosynthetics. Geosynthetic encased stone column as a composite structure, combines the features of both tension/ compression reinforcement, that improves the overall performance of stone columns, through a series of beneficial mechanisms like stress arching and soil confinement. The unit cell concept is widely used for most of the analytical solutions, nevertheless, the concept can also be easily applied in numerical analysis for complex situations, that might involve layered ground, rigid inclusion and various construction stages etc. Put this into the context, a unit cell model allows us to evaluate most of the geostructural behaviors within the influence zone of a single stone column, before we take to a full-scale problem modelling. Essentially through PLAXIS, evaluations, and thus comparisons can be drawn over various quantities for instance, stress concentration ratio, settlement and excess pore pressure dissipation, mobilized force and radial expansion of geosynthetic encasements, etc, that might concern practicing engineers.

The training session covers:

• Unit cell modelling in PLAXIS 2D & 3D
• Full-scale embankment problem modelling in PLAXIS 3D
• Evaluation of structural responses of stone columns, etc.
• Comparisons drawn over various quantities

Duration: 2 hour 17 minutes

Presented by: Xing-Cheng Lin