Abstract:

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{\epsilon }_{\mathrm{v}} increases nonlinear with the average stressp， and decreases with the ratio of bioenzyme-based soil stabilizer at p is constant. The test curves of {\epsilon }_{\mathrm{v}}-pare nonlinear relationship. ②The axial strain{\epsilon }_{\mathrm{1}}， lateral strain {\epsilon }_{\mathrm{3}} increases nonlinear with the deviator stress q respectively， and q increases with the ratio of bioenzyme-based soil stabilizer. The bulk strain{\epsilon }_{\mathrm{v}} decreases with the ratio of bioenzyme-based soil stabilizer. The test curves of q-{\epsilon }_{\mathrm{1}}、{\epsilon }_{\mathrm{1}}-{\epsilon }_{\mathrm{v}}、q-{\epsilon }_{\mathrm{3}} are hyperbola respectively. The stress-strain relationships between q and {\epsilon }_{\mathrm{1}} are strain hardening， and the relationships between q and {\epsilon }_{\mathrm{v}} 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{\sigma }_{\mathrm{3}}.

Key words: road engineering, bioenzyme-treated expansive soil, constitutive model with double yield surfaces, Lade model, elasto-plastic stress-train relation