Numerical Simulation of Ground Improvement using Stone Column in Silts-Paper

Paper

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The study uses PLAXIS 3D finite-element modelling to assess vibro-stone columns for improving silty soil beneath a raft foundation at a residential site in Ghaziabad. The model represents layered soil, a 35 m × 20 m raft founded 2.5 m below ground, and a 500 mm granular blanket. The columns are 500 mm in diameter, 12 m long, and arranged in a triangular pattern. A 150 kPa load is applied.<br /><br />Stone columns substantially reduced predicted settlement: from 298.5 mm in untreated soil to 62.68 mm after treatment, a reduction of approximately 79%. The results support the use of stone columns to improve foundation performance, although the study also notes that the stiffness of the supporting strata matters and that columns should extend to hard ground where possible.<br /><br />Parametric analyses found that settlement generally decreased as column diameter increased. For diameters from 500 mm to 1,000 mm, settlement fell from 19.26 mm to 9.925 mm—about 48.5%. Varying column length from 8 m to 16 m produced a less uniform trend: settlement peaked at 12 m and then declined.<br /><br />A simplified liquefaction assessment for the top three soil layers reported factors of safety between 1.77 and 2.65, indicating that the layers were not susceptible according to the study’s stated criterion. The paper nevertheless presents stone columns as a method for improving soil stability and addressing liquefaction-related concerns.<br /><br />Overall, the numerical results suggest that vibro-stone columns can considerably reduce settlement, with column diameter and founding-layer stiffness being important design considerations.

Keywords

PLAXIS 3D

vibro-stone columns

settlement reduction

raft foundation

silty soil

Ghaziabad site

finite element modelling

liquefaction assessment

column diameter

granular blanket