Research On Constitutive Model Of Unsaturated Compacted Loess

Based on reading and analyzing a large number of documents, and the unsaturated triaxial test data about compacted loess of lanzhou kyushu sets, analyzed deformation and strength properties about compacted loess under four kinds of stress path, given values of Alonso elastic-plastic model's parameters, and established the revised equation for Duncan-chang model applied to Compacted loess mechanical properties, some results obtained from the research are showed as follow:(1)Analyzed the deformation,strength properties about compacted loess under four kinds of stress path.In the process of compressed-rebound-repressed test, compression index would increase as Eventually confining pressure increase while expansion index would decrease;In the process of Triaxial consolidation drainage shearing test that both control suction and net confining pressure as constant, there exist a phenomenon that fist shear dilatation and then shearing expansion;For the same suction, the higher net confining pressure, the greater shear dilatation value; For the same net confining pressure, the higher suction and also the greater shear dilatation value. Meanwhile, for the same suction, the higher net confining pressure, the greater the shear strength; For the same net confining pressure, the the higher suction, also the greater shear strength;In the process of compression that controlled suction, the Yield stress would increase as suction increase, compression index would decrease while suction increase, and spring back index does not change significantly with suction;In the process of shrinkage that controlled the net mean stress, there exist the shrinkage deformation for compacted loess under the effect of suction; As the suction increase, yield stress does not change significantly, and can be regarded as constant.(2)Described the unsaturated mechanical properties of compacted loess with Alonso model, calculated the parameters' value, Fitted the v-logp and v-logs relation curves of compacted loess, Given yield surface equations in (p, q, s) stress space of compacted loess, and Mapped the space yield surface graphics of compacted loess, the results show that the Alonso model can well reflect the mechanical properties of compacted loess.(3)Apllied Duncan-chang model to the unsaturated mechanical properties of compacted loess, the results showed that Duncan-Chang model cannot fully describe the process of compacted loess that first strain-hardening and then strain-softening.Through introducing the slope modification coefficient k improved (σ1,—σ3)-ε, curve equation; Through the linear equation and transform Lorentz equation, puted forward two methods,instead Duncan-Chang hyperbolic relationshipε1-ε3 curve equation with two new equations. Based on the hypothesis that equation parameters and the suction,confining pressure accored with binary linear regression, thus extended uncan-Chang model to unsaturated soil range.The relationship expressions between equation parameters and the suction, confining pressure was fitted, madecurved shel of equation parameters in the suction-confining pressure space,meanwhile, gived parameters of two fixed Duncan-Chang model.The revised model was used to study the wetting deformation and received the conclusion as showed:The wetting deformation is greater as the soil suction is smaller; Net confining pressure also influence wetting deformation considerably, with net confining pressure increase, the wetting deformation would decrease; When net confining pressure keep constant, the higher the partial stress, the greater wetting deformation. Along with the increase of net confining pressure, the influence of suction to the wetting deformation would become smaller, and the unsaturated stress-strain curve would become more and more focused.