Constitutive relation with double yield surfaces of bioenzyme⁃treated expansive soil based on Lade model

The elasto-plastic stress-strain behaviors with double yield surfaces of bioenzyme-treated expansive soil was studied based on Lade model. Firstly, a series of the isotropic consolidation drainage tests and the triaxial consolidated drained shear tests of bioenzyme-treated expansive soil under different ratio of bioenzyme-based soil stabilizer were conducted. Secondly, the expressions between the parameters of the Lade model and the ratio of bioenzyme-based soil stabilizer were fitted based on the triaxial test results. Finally, a Lade model based on the ratio of bioenzyme-based soil stabilizer was proposed. The study conclusions as follows: ①The bulk strain εv increases nonlinear with the average stress p, and decreases with the ratio of bioenzyme-based soil stabilizer at p is constant. The test curves of εv-p are nonlinear relationship. ②The axial strain ε1, lateral strain ε3 increases nonlinear with the deviator stress q respectively, and q increases with the ratio of bioenzyme-based soil stabilizer. The bulk strainεv decreases with the ratio of bioenzyme-based soil stabilizer. The test curves of q-ε1, ε1-εv, q-ε3 are hyperbola respectively. The stress-strain relationships between q andε1 are strain hardening, and the relationships between q and ε1 are shrinkage. ③A Lade model based on the ratio of bioenzyme-based soil stabilizer can better describe the effects of the ratio of bioenzyme-based soil stabilizer on the elasto-plastic stress-strain behavior of bioenzyme-treated expansive soil, and can well predict the stress-strain relationship of bioenzyme-treated expansive soil under different ratio of bioenzyme-based soil stabilizer and confining pressures σ3. © 2021, Jilin University Press. All right reserved.