Vibro Stone Columns with Preloading – An Effective Foundation Solution for Large Storage Structures-PPT Presentation

PPT Presentation

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The presentation describes the use of vibro stone columns (VSCs) combined with preloading to support a large mounded LPG storage facility on challenging coastal soils near North Chennai.<br /><br />The project comprised three 450-tonne mounded pressure vessels. The mound covered approximately 1,350 m², was about 9.3 m high, and imposed a load of roughly 155 kPa. Long-term settlement after hydrotesting was limited to 50 mm. The subsurface included soft, compressible silty clay prone to consolidation settlement and low bearing capacity, over loose silty sand with liquefaction potential.<br /><br />The ground-improvement scheme used dry bottom-feed VSCs, 900 mm in diameter, installed to 12 m below ground level at 2 m spacing in a triangular pattern. The area replacement ratio was 18%. Preloading supplemented the columns, with surcharge equivalent to 60% of the total loading intensity.<br /><br />Settlement was monitored throughout surcharging and the holding period. The surcharge was removed after Asaoka’s method indicated a 90% degree of consolidation. Single- and group-column load tests showed settlements at design loads within allowable limits.<br /><br />The case study concludes that VSCs combined with preloading can address consolidation and settlement challenges for large storage structures on soft soils. The columns’ drainage effect accelerates consolidation, while also helping reduce liquefaction risk in underlying loose saturated sands.

Keywords

vibro stone columns

preloading

mounded LPG storage

coastal soils

consolidation settlement

liquefaction risk

soft silty clay

ground improvement

Asaoka method

settlement monitoring