Study on tropical organic soil stabilization based on biogrouting

Biogrouting is a new environmental friendly stabilization method to stabilize soft soils by applying microorganisms. The microorganisms produce CaCO3, which fill voids of soil particles and bond the particles. This work studied biogrouting of high plasticity tropical organic soil applying Bacillus subtilis bacteria. In order to study the effectiveness of biogrouting using Bacillus subtilis, unconsolidated undrained triaxial and direct shear tests were conducted on the untreated and stabilized soils. The curing time for the stabilized soil specimens were 7, 14 and 28 days before the tests were conducted. In order to study the influence of the amount of Bacillus subtilis, 6 ml and 12 ml of Bacillus subtilis liquid culture was injected into the soil specimens. The soil became stronger as the amount of Bacillus subtilis used increased. The results indicated that the longer curing time and the higher amount of Bacillus subtilis reflected better soil improvement in term of cohesion, friction angle and shear stress. After 28 days of curing time, injection of 6 ml and 12 ml Bacillus subtilis liquid culture increased the effective stress cohesion values by 180% and 270%, respectively.