Model tests on biogrouted granular columns in soft soil

This paper examines the possible use of a bio-cementation process to reduce excessive bulging that occurs during the loading of granular columns in soft clays. A 12-phase percolation bio-chemical treatment technique was used to bio-cement part of the columns targeting the columns upper section, where bulging usually occurs. Upon application of unit cell surface loads up to 350 kPa, placement of a bio-cemented granular column substantially reduced the vertical strains by 43% to 48% compared with an un-cemented granular column and 56% to 60% compared with unreinforced kaolin clay for just a low replacement ratio of 11%. Bulging was reduced by 62% to 75% following bio-cementation and mostly occurred where bio-cementation was less evident. Scanning electron microscopy and energy dispersive spectroscopy validated the existence of calcium carbonate. This study presents a relatively new alternative to reducing bulging in granular columns using a promising approach.