Performance of Stone Columns in Soft Clay - A Comparative Study of Bearing Capacity of Soil Estimated using IS Code Method, Actual Field Load Tests and Observations from Numerical Model

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Video Summary

Prakriti Krishna presents a case study on ground improvement for a cancer-care hospital in Jorhat, Assam, where soft clay, high groundwater and seismic risk posed foundation challenges. Soil investigations found about 13.5 m of soft clay, with estimated bearing capacity below the project’s requirement and predicted raft settlement exceeding limits. The team installed 1,170 dry, bottom-feed vibro stone columns, each 900 mm in diameter and approximately 9 m long, on a 2 m grid. Installation took 42 days.<br /><br />Single- and group-column plate load tests showed settlements within allowable limits. Because plate tests could not represent the full raft or long-term consolidation, the team also used PLAXIS 2D modelling. The predicted maximum settlement was 50 mm, within the 75 mm project limit, indicating the treatment was effective.<br /><br />Key lessons included planning drainage and rig movement, validating improvement after installation, and allowing for greater aggregate consumption than theoretical estimates—typically 10–20% extra.

Keywords

ground improvement

vibro stone columns

soft clay foundation

PLAXIS 2D modelling

settlement analysis