Microbialinduced calcite precipitation (MICP) is a technique that can be a potentialmethod to solve wetting swelling and drying shrinkage of expansive soils. Withthe bacteria concentration and urease activity as standards of measurement

thegrowth properties of Sporosarcina pasteurii in various conditions were studied

and the most favorable temperature

pH and vibration velocity were determined.Two different types of expansive soils were treated with MICP

and the effectof this method was studied by comparing expansive properties

cohesive force

internalfriction angle and shear strength before and after the treatment. The mechanismof MICP treated expansive soils was explained through microstructureperspective. The results showed that the optimal culture conditions for thebacterial growth were as follows: the pH of 7

the vibration velocity of 200 r/min

and the temperature of 30 ℃. After treating with MICP

the free swelling ratio and unloaded swelling ratio were decreasedsignificantly

while the cohesive force

internal friction angle and shearstrength were increased. The calcium carbonate generated during MICP played therole of pore filling and soil particle cementation

and the replacement of lowvalence cations by calcium ions and the wrapping effect of calcium carbonate onsoil particles improved the properties of expansive soils. The research canprovide beneficial references for the technology and engineering applicationsof MICP treatment of expansive soils.