Ground Improvement using Stone Columns to Mitigate Liquefaction Potential of Fine Sand by Wet Top Feed Vibro Replacement Method

Video Transcription

Video Summary

V.S. Parameshwaran presents a ground-improvement case study for construction sites in Assam, where saturated, loose-to-medium-dense fine sand and a high groundwater table created significant liquefaction risk under anticipated magnitude-7 earthquake shaking. Soil analysis indicated potential liquefaction to about 9.5 m depth.<br /><br />The project used vibro-replacement stone columns beneath building foundations. Columns 0.9 m in diameter, spaced 2 m apart in a square grid, were installed to an average depth of 7 m, with a 500 mm compacted sand blanket. The treatment covered approximately 3,835 m² and used a 16% replacement ratio. Grain-size testing showed fines below 10%, supporting the suitability of vibroflotation.<br /><br />Post-installation SPT results showed values increasing by two to three times, and cyclic resistance improved, indicating reduced liquefaction potential. The speaker concludes that stone columns were technically viable and economical, while emphasizing the need to plan for substantial slurry disposal during wet installation.

Keywords

liquefaction

stone columns

vibro-replacement

ground improvement

Assam