Improvement of soft soils using bio-cemented sand columns

This paper discusses the results of small-scale model tests that were undertaken to investigate the behaviour of un-cemented and bio-cemented coarse sand columns installed within a soft clay bed. The tests also focused on studying the effect of biocementation to reduce excessive radial expansion and settlement that may occur during installation or loading of sand columns. A multi-phase biochemical treatment strategy was used to obtain a partial biocementation, in particular at the upper section of the sand column where bulging usually occurs. The results show that the partially bio-cemented sand column substantially reduced vertical strains which were in the order of 71% and 97% compared with un-cemented sand column and kaolin clay, respectively. The bulging of the bio-cemented sand column was associated with the bottom section of the column where there were no or less bio-cemented materials.