Dynamic modulus and dynamic strength of liquefaction silt bio grouted by iron oxidizing bacteria were measured by dynamic triaxial test. Results show that dynamic modulus and dynamic strength were improved obviously after several times of bio grouting. Scanning electron microscopy(SEM) and X ray diffraction(XRD) were used to analyze the modification mechanism. Microscopic analyses show that metabolites of iron oxidizing bacteria contain ferrum oxydatum phosphate complexes which has excellent adsorptivity and flocculation efficiency. The iron based complexes could adsorb free cations and polysaccharide product in silt, and ultimately deposit into biological slime to fill the voids between soil particles and glue them, thereby increase the dynamic shear behavior of silt.
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