Research On The Viscoelastic-Viscoplastic-Damage Model Of Structural Soft Soil

The structural and rheologic properties are differently intrinsic characteristics of soft soil. In the past, constitutive models of soil used in the soil numerical analysis were considered respectively. In fact, the structural and rheologic properties exist simultaneously. Additionally, the construction disturbances existing in the method of surcharge preloading for soft clay gourmand can cause the decline of shear strength and increase of deformation. The inferences on the structural property and deformation due to the initial disturbance were not considered or could not be quantitatively analyzed in the past calculation. So, it is important to carry on the research about constitutive model considered the structural and rheologic properties of soft soil.A modified viscoelastic-viscoplastic-damage constitutive model of soft soil has been developed in this thesis, in which the structural and rheologic properties of soft soil can be taken into account simultaneously. It is introduced into FEM program of Biot consolidation theory, indicating that the long-term deformation of soft soil can be calculated. The initial disturbance and the gradual damage of soft soil can be quantitatively analyzed in soil deformation. During the research, several mainly relating work have been carried on as the follows.1. Based on a viscoelastic-viscoplastic constitutive model of soft soil suggested by ZhanMeiLi, ZhaoWeiBin and etc., which was developed based on Yin's double yield surfaces constitutive model, instantly elastoplastic deformation of soft soil and a varient reflecting the damage rule have been introduced into the model. Thus, a viscoelastic-viscoplastic-damage constitutive model has been developed, which can reflect the structural and rheologic properties of soft soil simultaneously.2. The model has been coded into FEM program of Biot consolidation theory, and a mathematical expression of nonlinear FEM solution has been deduced in this thesis, which is related to the viscoelastic-viscoplastic-damage model.3. The solutions of FEM program and some key problems in the process have been introduced and analyzed. A FEM program about the viscoelastic-viscoplastic-damage deformation of soft roadbed under plane strain consolidation has been coded.4. The methods on numerical simulation in disposal of soft highway roadbed have been introduced. And the numerical simulation about a certain testing segment of a highway roadbed has been carried with the FEM program.Meanwhile, three different cases in the deformation of soft soil------the soft soil isanalysed with viscosity and damage, the deformation is calculated with no damage but viscosity, and the deformation is considered without viscosity and damage------have been calculated and analysed respectively. The infulences ofinitial damage have been stitudied and it has been compared with actual detas. The viscoelastic-viscoplastic-damage model and the method of analysis proved to be reasonable and effective.