Performance of Stone columns in multi-layered soils under the action of Seismic loads-Paper

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The study evaluates stone columns as a seismic ground-improvement method in layered soils, focusing on their effects on excess porewater pressure (EPP), acceleration, settlement, and cyclic stress. The authors used PLAXIS 2D finite-element analysis with a small-strain hardening soil model. The modeled profile comprised dense sand over soft clay and stiff clay; stone columns 0.8 m in diameter, spaced 1.7 m apart, extended to 27 m depth. An earthquake record from the 1979 Imperial Valley event was applied at the base of the model. The numerical approach was checked against results from a shaking-table experiment.<br /><br />Stone columns generally reduced EPP and vertical deformation, with the clearest EPP reduction in the soft-clay layer, where the columns’ permeability shortened drainage paths. Effects were smaller in dense sand and stiff clay. The columns also reduced settlement by reinforcing the ground: in the multilayered site profile, maximum settlement decreased by about 53%. Acceleration reduction was modest in the layered profile, and the cyclic stress ratio changed little overall, although the columns carried more shear stress than the surrounding soft clay.<br /><br />The findings indicate that stone columns can reduce seismic pore-pressure buildup and settlement, particularly in soft cohesive layers. Their effectiveness varies with soil stiffness and depth, and the authors note that further investigation is needed to better establish performance in multilayered soils under earthquake loading.

Keywords

stone columns

seismic ground improvement

excess porewater pressure

layered soils

PLAXIS 2D

small-strain hardening soil model

settlement reduction

earthquake loading

soft clay

cyclic stress ratio