Numerical Analysis For Mechanical Behavior Of Cohesiveless Soil Based On Cloe Hypoplastic Theory

Cohesiveless soil is one kind of granular soil including sandy soil, gravel, rockfill material.It has been widely used in highway subgrade, building foundation, and hydropower engineering for its accessibility,high strength and high permeability. Its mechanical property affects directly because it sustains most loads of the building for its role of the main structure.Practicability and durability of such structures directly depend on the mechanical property of cohesiveless soil because it sustains most part of loads. The physical and mechanical properties of cohesiveless soil are very complex.How to develop a more comprehensive and more accurate constitutive model is a challenge for researchers.After summarizing some different constitutive models from domestic and foreign, the basic framework and the mechanical properties of the hypoplastic theory were expounded. The CLoE model which is a representative model in hypoplastic theory was thoroughly studied.The improved researches of CLoE hypoplastic model were discussed as a key role. The main contents in this dissertation are as follows:(1) Some mechanical characteristics, such as gradation, compaction index, shear strength and dilatancy of cohesiveless soil were expounded and summarized.(2) Different constitutive models for cohesiveless soil from domestic and foreign were compared detailly. The hypoelasticity model and elastoplasticity model were thoroughly discussed. The theory and mechanical properties of geotechnical material were analysed.(3) The theoretical basis of hypoplastic model was expounded. The classics elastic-plastic model and hypoplastic model were compared from the aspects of establishment methods and form of model and mechanical property.The advantages of hypoplastic model at modelling cohesiveless soil were raised.(4) For K and CLoE type of hypoplastic model,the features and defects of modelling geotechnical materials were thoroughly discussed. The creative construction method was expounded detailly. The advantages of CLoE theory in simulating triaxial tests、dilatancy irreversibility were analyzed. And the disadvantages of CLoE theory in simulating cyclic loadings wetting effect and anisotropy were also raised. The code of CLoE was developed on ABAQUS platform.A verification of the code was conducted from the veracity and adaptation.(5) To compare CLoE and Gudehus-Bauer hypoplastic model,a series of finite element analyses were carried out on modeling the strain localization for Hostun sand under plane strain condition. The strain localization was analyzed mainly in different confining pressures and same initial imperfection. Numerical results suggest that CLoE model performs better than Gudehus-Bauer model in modeling strain localization. Influence of confining pressure and initial imperfection can be considered by CLoE hypoplastic model.(6) Application of hypoplastic model to cyclic stressing or deformation with small amplitudes reveals a striking shortcoming, called ratcheting. The features of intergranular strain were expounded detailly. The so-called intergranular strain was introduced to CLoE hypoplastic model to extend hypoplasticity to improve the behavior of dense sand under cyclic loading. The intergranular rate and the maximum intergranular were improved to overcome the difference between modified model and CLoE model in the same monotonous load. Numerical results suggest that, the modified model can retain the advantage of overcoming ratcheting. What’s more, the consistency of the modified model and CLoE model can also be guaranteed in the same monotonous load.