Field investigation has shown that the excess pore water pressure induced by deep mixing column installation may be higher than the hydraulic fracturing pressure. The interaction behavior between the deep mixing column and the surrounding soil can be simulated as the shearing-expanding process of a cylindrical cavity. An approach is proposed to analyse the soil fracturing due to tensile force. Analytical results indicate that the rotation of the mixing blades has a significant effect on the clay fracturing in a close region around the column. The proposed method has been verified against laboratory test. Fracturing cracks have two functions: firstly

cement slurry can flow into the fracturing crack; secondly

excess pore pressure may dissipate through fractures. These two effects speed up the strength recovery of the surrounding soil.