The purpose of this study is to establish a modified Yin’s double-yield-surface model based on the ratio of bioenzyme-based soil stabiliser

which can accurately describe the physical and mechanical properties of the bioenzyme-treated expansive soil. A series of drained triaxial shear tests was carried out to study the evolution laws of stress-strain

the elastic deformation

yield surface shape

dilatant yield surface

and failure line equation relating to the content of bioenzyme. Moreover

the effect of the bioenzyme content on the parameters of the Yin’s model was analysed. Finally

the bioenzyme content was introduced as a correction factor for the modified Yin’s double yield surfaces model. The results show that the bioenzyme can effectively improve the mechanical properties of the treated expansive soil. The modified Yin’s double-yield-surface model can well describe the constitutive relation of the bioenzyme-treated expansive soil. The theoretical calculation results of the modified Yin’s model show good agreement with the experimental results. Besides

the parameter determination method of the modified model is consistent with Yin’s original model.