Study On The Elasto-plastic Constitutive Model Of Structured Soil

The importance of research on the structure of soil is introduced firstly. And then the development of research on the structure of soil is reviewed, followed by the study on the fundamental behavior of structured soil based on the experimental data. An elasto-plastic constitutive model which can simulate the strain softening and strain hardening is presented.By putting some amount of cement into soil sample, structured soil with macro-pores is prepared. A series of tests are carried out on the man-made structured soil samples. It is clear from the test results that the mechanical properties of natural structured soils can be well duplicated by the man-made structured soil.Based on the compressive test on different stress paths, the initial yielding curve is confirmed base on the yielding stresses of a certain stress paths, as well as the direction of the increment of plastical strain. Plastical work is used as the hardening parameter to determine the hardening rule.The structured elasto-plastic model is proposed based on the experimental data without some hypothesis as the classical plastical theory, which makes the model more reasonable..It can be instructed from the test that the structured soil has an initial yielding curve in which is characterized by the elastical properties. When the confining pressure is less than the yielding stress the peak stress rise and strain softening aggravates with the increase of cement. In addition, the stress tends to be similar when the cement is damaged completely.Furthermore the research on the FEM modeling of strain softening material is reviewed followed by the introduction of a FEM modeling based on the displacement-controlled method.A typical example for the shallow base on the natural soil is analyzed by the proposed structured model and that by the Cambridge model for comparison with FEM. it is showed that the result is reliable.